Fix BTS attribute requests

* fix BTS numbers: use 0 to indicate given BTS and 0xFF to indicate all
  BTS' as it's explained in 3GPP TS 52.021 ยง9.3.
* only request attributes from supported (OsmoBTS) types

Change-Id: I8f43055c38000248033a8ff9ddaf0910d68d794b
Related: OS#2317
2 files changed