CI: fix flexran-rtc build Xenial

See merge request oai/openairinterface5g!1007

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

MR991: Remove hack in LTE PDCP for noS1 mode  
- Removes a hack which was used when LTE PDCP was used for NR in noS1 mode

MR993: UL and DL fixes LDPC short codewords 
- Fix UL & DL LDPC decoding for short LDPC code, e.g. Z_c is not multiple of 8
- Fix DLSCH data transmission with multiple DMRS symbols per slot
- small TA fixes on OAI 5G NR UE
- Implemented CQI measurement at NR UE
- NR UE cleanup 

MR1000: doc: fix build directory in BASIC_SIM.md

MR960: 256 QAM demodulation routines  
- Added functions for demodulation of 256 QAM signals.
- Added a command line flag to enable mcs table entry in PDSCH-Config in RRC to use 2nd MCS table for PDSCH.
- Added an option for using 256 QAM mcs table in nr_dlsim.

MR989: Docker and Deployment improvements (CI)  
- Image generation for eNB --> template for configuration files and dedicated entrypoint in Ubuntu
- Docker-compose-based EPC deploy
- Traffic test fully validated using the `trf-gen` container
- Flexran-rtc support when deployed in a container (Not fully done for the X2 Handover part)
- Added docker-compose-based eNB deployment
- Retrieve logs for such eNB deploymnent 
- Functional and log  update of nsa fr1 test but valid for gNB terminate also (enhanced ping stats and gNB markers)

MR992: Fix data transmission in "do-ra" mode
- UL and DL Traffic works now in do-ra mode, but there are still some PUCCH issues remaining. These issues are harming the acknowledgement of DL packets, and thus leading to unnecessary retransmissions.
The relevant warnings at UE are:
`PUCCH Invalid pucch resource indicator: at line 1082 in function select_pucch_resource of file openair1/SCHED_NR_UE/pucch_uci_ue_nr.c`
and
`PUCCH Error for number of bits for acknowledgment : at line 909 in function get_downlink_ack of file openair1/SCHED_NR_UE/pucch_uci_ue_nr.c`
Note: UE needs rbconfig.raw and reconfig.raw files from the *currently* running gNB, as the C-RNTI is random and different for each run.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

rfsimulator: do not show "gap in reception" messages if complete slots are skipped (e.g. NR DL: gNB transmission, UE reception)

# Conflicts:
#   openair2/LAYER2/NR_MAC_gNB/gNB_scheduler.c
#   openair2/LAYER2/nr_pdcp/nr_pdcp_oai_api.c

MR969: Develop oriecpriupdates  
Makes IF5 functionality compatible with ECPRI user-plane. 
Control-plane functionality for supporting third-party RRUs : provides an interface converting OAI-native RF parameters, a subset of LTE framing parameters, and RF streaming activation/deactivation to a wrapper (libthirdparty_transpro.so) which uses the proprietary interface of the RRU. 
This branch was tested with a commercial eCPRI RRU from AW2S.

MR980: Nr ul scheduler basis 
- cleanup of UL scheduler, and add interface preprocessor-postprocessor (in `NR_UE_sched_ctrl_t`)
- Postprocessor can (almost) handle multiple UEs. Preprocessor will follow soon (proportional fair scheduler)
- Preprocessor for phytest (always schedule 50 RBs due to OAI UE limitations) and real UE (as many resources as possible)
- Internal structures have been updated: the `UL_tti_req` structure became an array (as `UL_tti_req_ahead`) so that we can schedule in advance and mark resources as used. Before, we would keep the corresponding nfapi message structure per UE, which could get messy when we have many UEs.

There are no functional changes (UL/DL performance is the same). 

MR987: Nr phy mac if multi ue  
- Handles multiple UEs in `NR_IF_interface.c`
- Some minor clean up

MR979: Pusch decoder threads parameter  
- Added a config file parameter for specifying the number of threads to be used for PUSCH decoding.

MR982: nr pdcp: use pdcp config
-There was a problem with SN size. It was hardcoded to 12 bits (so max sn = 4095) but we configure the UE with 18 bits. 
Get the correct value from pdcp_Config.
- Store also discard_timer and t_reordering that will be used later by a proper NR PDCP layer 

MR984: NR FR2 SSB
- several fixes mainly concerning FR2 synchronization and RA both at gNB and UE
- SSB RRC signaling for FR2
- Coreset RRC for FR2
- SSB detection in FR2 for SSB index > 15
- Adjust sync function issue
- Fix for scheduling of MSG2 (issue with sl_ahead)

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Conflicts:
	openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c