tests: don't rely on strerror text when testing rmdir failure

AIX doesn't make a distiction between EEXIST and ENOTEMPTY; relying
on the strerror string for the rmdir failure is fragile. Just test
that the start of the string matches the Git controlled "failed to
rmdir..."  error. The exact text of the OS generated error string
isn't important to the test.

Signed-off-by: Charles Bailey <cbailey32@bloomberg.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3600-rm.sh

@@ -711,8 +711,7 @@ test_expect_success 'checking out a commit after submodule removal needs manual
 	git submodule update &&
 	git checkout -q HEAD^ 2>actual &&
 	git checkout -q master 2>actual &&
-	echo "warning: unable to rmdir submod: Directory not empty" >expected &&
-	test_i18ncmp expected actual &&
+	test_i18ngrep "^warning: unable to rmdir submod:" actual &&
 	git status -s submod >actual &&
 	echo "?? submod/" >expected &&
 	test_cmp expected actual &&

t/t7001-mv.sh

@@ -446,8 +446,7 @@ test_expect_success 'checking out a commit before submodule moved needs manual u
 	git mv sub sub2 &&
 	git commit -m "moved sub to sub2" &&
 	git checkout -q HEAD^ 2>actual &&
-	echo "warning: unable to rmdir sub2: Directory not empty" >expected &&
-	test_i18ncmp expected actual &&
+	test_i18ngrep "^warning: unable to rmdir sub2:" actual &&
 	git status -s sub2 >actual &&
 	echo "?? sub2/" >expected &&
 	test_cmp expected actual &&