gsm_04_08_cc: Add global guard timer for MNCC

The external MNCC handler may hang indefinitely in cases where the remote
end of the MNCC ceases to work properly. Add a global guard timer to
make sure the call reaches ACTIVE state.

Change-Id: I7375d1e17cd746aac4eadfe1e587e82cf1630d3d
Related: OS#3599
6 files changed