Ip table clean use to run on oaisim shutdown. It is moved to run on oaisim starts.

In openairinterface5g many definitions in many layers of UE or eNB NB_MAX.
We created a file called openairinterface5g_limits.h
located at openairinterface5g_dir/targets/COMMON/ declaring the number max
of UE and eNB to be used in ALL layers depending on launching conditions
(LARGE_SCALE for example).

When using abstraction mode, layer2_init_UE() and openair_rrc_ue_init()
are called according to first_sync state and only without MME support.

We added the global variable abstraction_flag to allow abstraction mode
when MME is enabled.
Openair2 is also used in lte-softmodem, so it must have a global variable
abstraction_flag. So we moved it out from the main() scope.

This commit reverts behaviour of data generation as before
commit 7207c65b05fd812a18371827f2bfb1431fc58696:

    fix .ue* filenames in scripts and documentation

    TODO add option to conf2uedata and adapt script

This remove the old static lists

There was a side effect corrupting data because hplmn_index was not computed.

TODO add option to conf2uedata and adapt script

This patch adds the conf2uedata tool for generating .ue.nvram* .ue.emm.nvram*
and .usim.nvram* files from a textual configuration file.

The configuration file define most usefull values like plmns, mnc, mcc, msin, K,
OPc for several users.
The files generated will always ends with a number corresponding to the user
entry in the configuration file.

This breaks oai5g because other script have not be updated for using
conf2uedata.
This breaks also the at_nas_ue command.

Examples of configuration files are in openair3/NAS/TOOLS/