fstests: fix group check in new script

In the tests/*/group files, group names are found in the Nth columns of
the file, where N > 1.  The grep expression to warn about unknown groups
is not correct (since it currently checks column 1), so fix this.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

new

@@ -243,10 +243,7 @@ else
     #
     for g in $*
     do
-	if grep "^$g[ 	]" $tdir/group >/dev/null
-	then
-	    :
-	else
+	if ! grep -q "[[:space:]]$g" "$tdir/group"; then
 	    echo "Warning: group \"$g\" not defined in $tdir/group"
 	fi
     done