Avoid selecting channels from administratively locked trx

Found while playing with "rf_locked 1" on a 2TRX setup with channel
allocator descend. After applying the setting, the 1st TRX is still used
to allocate the channels. After this patch is applied, the BSC correctly
allocates channels from TRX0.

Change-Id: I5201d2749363c9cbd0706177bde09117b163cbe3
4 files changed