xfstests: Improve test 219 to work with different filesystems

xfstests: Improve test 219 to work with different filesystems

Different filesystems account different amount of metadata in quota.
Thus it is impractical to check for a particular amount of space
occupied by a file because there is no right value. Change the test
to verify whether the amount of space is between the expected amount
of space and the expected amount +5%.  The number of files is
checked exactly as previously.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Alex Elder <aelder@sgi.com>