abis: Try one reconnect to previously connected BSC before trying next one
abis: Try one reconnect to previously connected BSC before trying next one

This way we keep all BTS connected to the same BSC if there was a
spurious network problem.

Related: SYS#4971
Change-Id: I16b75da5987584d099edc3a640f3a5cd61f3ad69

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts