Changes

bts: fix TC_rsl_ms_pwr_dyn_ass_updown: adjust the timers

This testcase predates major changes to the MS power control logic
in osmo-bts and was passing thanks to a coincidence (broken UL SACCH
cache in trxcon).  Specifically, the MS power loop is now using
P_Con_INTERVAL=4 by default.  This means that the power control
decision is intentionally delayed and a change may occur only once
in a period of 4 SACCH blocks (N=4 is ~1.92s).

Adjust the timer values to take this into account.  Take a chance
to move comments in-place and expand them with more details.

This patch makes TC_rsl_ms_pwr_dyn_ass_updown pass again.

Change-Id: I36d87c12f49ec13003b708d768285aa6840e81eb
Related: OS#6945