tests: mark two failing tests under FAIL_PREREQS

Fix a couple of tests that would potentially fail under
GIT_TEST_FAIL_PREREQS=true.

I missed these when annotating other tests in dfe1a17df9 ("tests: add
a special setup where prerequisites fail", 2019-05-13) because on my
system I can only reproduce this failure when I run the tests as
"root", since the tests happen to depend on whether we can fall back
on GECOS info or not. I.e. they'd usually fail to look up the ident
info anyway, but not always.

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

t/t0007-git-var.sh

@@ -17,7 +17,7 @@ test_expect_success 'get GIT_COMMITTER_IDENT' '
 	test_cmp expect actual
 '
 
-test_expect_success !AUTOIDENT 'requested identites are strict' '
+test_expect_success !FAIL_PREREQS,!AUTOIDENT 'requested identites are strict' '
 	(
 		sane_unset GIT_COMMITTER_NAME &&
 		sane_unset GIT_COMMITTER_EMAIL &&

t/t7502-commit-porcelain.sh

@@ -402,7 +402,7 @@ echo editor started >"$(pwd)/.git/result"
 exit 0
 EOF
 
-test_expect_success !AUTOIDENT 'do not fire editor when committer is bogus' '
+test_expect_success !FAIL_PREREQS,!AUTOIDENT 'do not fire editor when committer is bogus' '
 	>.git/result &&
 
 	echo >>negative &&