BTS_Tests: do L1CTL.clear in f_pcu_to_l1()

When calling f_pcu_to_l1(), the L1CTL port still contains many BCCH
related L1CTL DATA.ind messages in the queue.  It's not a really a
problem since they all get discarded, but still they're producing
lots of useless TTCN_MATCHING log messages.

Change-Id: I57b745bcfc48dc621359658cd43d2ee622fde49b
1 file changed