Changes

bts: TC_tx_power_ramp_adm_state_change: Fix Tguard too low sometimes triggering

One can see with the following failing output below that the Tguard is
too low:
"""
13:36:12.459089 5684 BTS_Tests.ttcn:2836 Reached full power, wating a bit more until success
13:36:12.459097 5684 BTS_Tests.ttcn:2837 Start timer T: 2 s
13:36:14.358525 5684 Misc_Helpers.ttcn:35 setverdict(fail): pass -> fail reason: ""BTS_Tests.ttcn:729 : Tguard timeout"", new component reason: ""BTS_Tests.ttcn:729 : Tguard timeout""
"""

Change-Id: I95448c732d08a30893cb958af79bf21c39ff10cb