tests: configure fsmonitor.mode=paranoid always if fsmonitor is used

This forces fsmonitor extension execute "paranoid" code path.

Strict speaking, we should make fsmonitor-run-tests.py accept own
specific options, but there is no code path, which is disabled in
"paranoid" mode, at least now. Therefore, this solution seems
reasonable enough.

tests/fsmonitor-run-tests.py

@@ -123,6 +123,12 b' def run():'
         runtestsargv.extend([
             '--extra-config',
             'extensions.fsmonitor=',
+            # specify fsmonitor.mode=paranoid always in order to force
+            # fsmonitor extension execute "paranoid" code path
+            #
+            # TODO: make fsmonitor-run-tests.py accept specific options
+            '--extra-config',
+            'fsmonitor.mode=paranoid',
             '--blacklist',
             blacklist,
         ])