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.