Send "BSSMAP CommonID" to tell BSC about the IMSI

We're already sending the RANAP CommonID message to the RNC,
let's do the same using BSSMAP CommonId towards the BSC.  This
way the BSC knows about the IMSI of the served subscriber, which
is very useful for logging/debugging.

Change-Id: I2552736477663adb250c55728093500e8ae83ebb
Closes: OS#2969
Depends: libosmocore.git I353adc1aa72377f7d4b3336d2ff47791fb73d62c
14 files changed