Reduce T3109 default from 19s to 5s

T3109 is started when the BSS sends a RR CHAN REL to the MS and stops
downlink SACCH generation. Stopped when the MS successfully releases the
LAPDm link. After stop or timeout, the radio channel is released using
RSL RF CHAN REL.

Recommended values in literature are 1-2s + RadioLinkTimeout*0.48s or
5s, while we had the absurdly high 19s timeout.  This means we occupy
the radio channel way longer than needed in situations where the MS is
no longer able to properly release Layer2 (LAPDm DISC) due to loss of
signal or the like.

See also: https://osmocom.org/projects/osmobsc/wiki/Timers

Change-Id: I7416b4118e5b73c6ffb98e3546bc62a36c7a967a
Closes: OS#2734
1 file changed