insertForUser takes a specified user and attempts to adjust that user's
settings, first looking at their existing settings to determine the difference.
However it was querying the settings for the calling user, rather than for
the user whose settings were being changed.
Also add a test that exercises the fix.
Change-Id: I6ed6fd79154ac1b6e6ab880769ac9081dfff6b80
d2726582f1