tests: take extra care for fsmonitor at enabling incompatible extension
This is worthwhile, because these tests don't focus mainly on using
incompatible extensions itself.
tests: remove meaningless entries from blacklist for fsmonitor
IMHO, these tests were listed up in blacklist at
3b67f27bb908, because
fsmonitor extension wasn't correctly installed before actual testing
at that revision (this issue was fixed by
776fd2e2cf5a).