Changes

nokia cosmetic: add bts_is_insite() function

Nokia InSite gets a different config than the larger Nokia BTS models,
and make_bts_config() function checks the BTS type to decide which
config to send.  Change the BTS type check from a long 'if' line that
compares against 3 different InSite BTS type codes to bts_is_insite()
helper function that encapsulates a switch statement.

Upcoming code additions will need to check for Flexi Multiradio BTS
family in a similar manner - so be consistent.

Change-Id: I44bbcd79d9741f1df280b6b2391f04f754598035