Changes

Fix wrong list entry derreference during bts_depend_find_entry()

Commit 92dc38d1c2b49efd0d4626e7ad5fb2db5ae7e5bc converted
bts->depends_on from bitmask to a list, but introduced an error while
doing so, iterating the wrong list and hence derreferring wrong entries
from it.

This caused for instance sporadic malfunction where osmo-bsc refused a
BTS from connecting with "Dependency not full-filled".

Related: SYS#7062
Related: SYS#7624
Fixes: 92dc38d1c2b49efd0d4626e7ad5fb2db5ae7e5bc
Change-Id: I50c8111d71ee4493076cd2cf3d4d850fee3c0414