Changes

msc: Fix TC_stat_bsc_sctp_disconnected expectancies

The test was passing when run alone, but was failing when run after
other tests using other BSCs/RNCs, since osmo-msc learned about them and
hence ran_peers.total was >1.

Change-Id: I22da7ae5c282a30e933f2f29b671ece8b6147ce9