Merge from Eurecom: develop branch

See merge request aburger/openairinterface5g!49

Separate nfapi.conf files for proxy

See merge request aburger/openairinterface5g!48

In scripts/conf_files, restore ue.nfapi.conf and nr-ue.nfapi.conf
to the template versions.  And add proxy_ue.nfapi.conf
proxy_nr-ue.nfapi.conf for use with emane.git's run-oai and
multi-ue-proxy.git's run-oai.

-fixes UL iperf log collection/analysis for UE module
-fixes iperf processes mgt for UE module

MR !1188 : NR_gNB_initial_MIB_fix  
This MR fixes a bug for which the gNB would send an empty MIB in the first frames of execution. This is because MIB is generated every 8 frames but the first MIB wouldn't be generated before frame 8 at the beginning of each run.

MR !1184 : x2_handle_sctp_shutdown
Avoid eNB exiting after gNB tries to reconnect over X2 for NSA

Found by -fsanitize=address

```
=================================================================
==35428==ERROR: AddressSanitizer: global-buffer-overflow on
address 0x0000021039a0 at pc 0x000000566dd6 bp 0x7ffc7974ccd0 sp
0x7ffc7974ccc0
WRITE of size 4 at 0x0000021039a0 thread T0
    #0 0x566dd5 in main
    targets/RT/USER/lte-uesoftmodem.c:629
    #1 0x7f36223cb83f in __libc_start_main
    (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)
    #2 0x582218 in _start
    (cmake_targets/ran_build/build/lte-uesoftmodem+0x582218)
```

nr-uesoftmodem crashes with a sanitize-address issue -- to be investigated.

Merge branch 'develop' of gitlab.eurecom.fr:oai/openairinterface5g into x2_handle_sctp_shutdown

Initial implementation of NR5G Standalone Access Registration procedures with CN5G.

Integration 2021 wk25

MR !1187 : improve UE module control
* improve UE module control
* make Qlog generation optional
* add nsa tests
* update jenkins pipeline

This reverts commit 0cd35686