mktag tests: run "fsck" after creating "mytag"

Change the last test in the file to run an "fsck --strict" after
creating the tag at the end.

We're just doing this for good measure to check that fsck behaves as
expected now that there's finally a reference for our valid tag. Other
tests going to be checking this elsewhere, but it's nice to cover all
the edge cases in this test to make it as self-contained as possible.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3800-mktag.sh

@@ -350,7 +350,8 @@ EOF
 
 test_expect_success 'create valid tag' '
 	git mktag <tag.sig >hash &&
-	git update-ref refs/tags/mytag $(cat hash) $(test_oid zero)
+	git update-ref refs/tags/mytag $(cat hash) $(test_oid zero) &&
+	git fsck --strict
 '
 
 test_done