xfstests: fix fsx fpunch test to actually test for fpunch

xfstests: fix fsx fpunch test to actually test for fpunch

The operation flags parameter to fallocate is the second parameter,
not the last. Hence the fpunch test is actually testing for falloc
support, not fpunch. Somebody needs a brown paper bag.

Also, add a ftruncate call whenthe fpunch succeeds just in case the
file was not already zero sized. Failing to ensure we start with a
zero length file can cause read ops to fail size checks if they
occur before the file is written to be the main test loop.

While there, observe the quiet flag the same as the falloc test
does and have them both emit the warning at the same error level.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>