fs-tests: integck: make -v work -e

fs-tests: integck: make -v work -e

Make the verify option -v work with power cut emulation option -e. We can
verify all operations except of writing to the file, because of write-back.
Indeed, even if we write successfully, the pages may still be in the page-cache
and if an emulated power cut happens they will be dropped, and our verification
will fail.

I am not 100% sure it is save to verify non-write operation in other FSes, but
only UBIFS has power cut emulation mode now, so we do not really care about
other FSes at this point.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>