Changes

gsm_bts_num(): use hashtable to lookup bts

gsm_bts_num() is mostly used to lookup bts object from its nr in VTY and
CTRL interfaces.
However, it's also used in hotter paths like pcu_rx().
It is also used during local neighbor resolution, mostly at startup or
when the VTY is re-applied from CTRL interface.

Related: SYS#7062
Change-Id: I7312da7d9aa80c6d0f2e92e9c7d20d32ce453ad1

tests/ctrl/osmo-bsc-neigh-test.cfg: Fix duplicate <LAC,CI> between bts1 and bts2

According to TS23.003, CI should be unique in a LAC.
Previous commit wrongly introduced a while ago a new "bts 2" with same
LAC and CI as "bts 1" in config file.

This makes current tests fails once a hashtable is added to lookup bts
by lac, since the hashtable code does prepend new bts instead of
appending them. As a result, bts 2 is returned instead of bts 1 being
previously returned.

Also change the ARFCN+BSIC since it was also duplicated. It makes not much
sense to have 2 neighbor BTS with same ARFCN+BSIC.

Fixes: 97ed3c8d971f3c231a1303efe61b3f98116f1e2f
Change-Id: I7d1ebd529e050ecb4c14b9d3523637e4c8c87e1d