Previously si2quater SI messages were always scheduled. Check for
neighbor configuration and only schedule si2q when necessary. Add
corresponding unit test.
Change-Id: Ibe997803ffb894133fd4d838410fe735791d414f
Fixes: OS#1727
Reviewed-on: https://gerrit.osmocom.org/81
Tested-by: Jenkins Builder
Reviewed-by: Holger Freyther <holger@freyther.de>