tweak fsm_msc_mgcp FSM and FI name

Instead of

  MGW(MGW_99)

use a name of

  msc-mgcp(MSISDN:2331_GERAN_A:00000017_trans99)

1. The FSM is communication towards an MGW, not the MGW itself. When reading
combined logging (gsmtap_log), it is confusing to read 'MGW' in a log coming
from the MSC. The API is also called msc_mgcp_*.

2. Calling the FSM instance 'MGW_' again doesn't make sense.

3. Indicate 'trans' before the trans_id (trans_id was already shown, but not
indicated what it was).

4. Also indicate the actual subscriber's identification.

5. Also indicate the RAN connection and conn_id.

This comes up while trying to understand a call coming in on an already
established call: parsing the log with a human brain is near torture without
this info, taking extremely long to get grips on.

Change-Id: Ie5fc1ffb7eba0209fee4666a075655cd24d27473
1 file changed