BTS_Tests: do not connect to PCUIF socket if not used

The PCUIF connection involves a lot of frequent messages, such as
the TIME.ind and since recently DATA.ind with len=0.  As a result,
the test suite logs are getting unreadable due to lots of coding
warnings and port queueing notifications.

This change is aimed to improve the situation a bit, by establishing
the PCUIF connection only for those test cases which actually use it.

Side effects:

  * TC_pcu_socket_verify_info_ind becomes reliable, because the
    PCUIF establishment is done after the RSL bootstrapping;

  * TC_pcu_socket_connect_multi starts to fail, because it used
    to pass due to timeout, since not all messages are handled
    in the 'alt' statement.

Change-Id: I09ccb65ce94a41ffdad4e93da650c3f32d422af4
Related: OS#5083
2 files changed