git p4 test: fix badp4dir test

The construct used to get the return code was flawed, in that
errors in the &&-chain before the semicolon were not caught.  Use
the standard test_expect_code instead.

Set PATH in a subshell instead of relying on the bashism of
setting it just for a single command.

And fix the grep line so it doesn't worry about grep segfaults,
and doesn't fail for i18n issues.

Reported-by: Johannes Sixt <j.sixt@viscovery.net>
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9800-git-p4-basic.sh

@@ -134,9 +134,13 @@ test_expect_success 'exit when p4 fails to produce marshaled output' '
 	exit 1
 	EOF
 	chmod 755 badp4dir/p4 &&
-	PATH="$TRASH_DIRECTORY/badp4dir:$PATH" git p4 clone --dest="$git" //depot >errs 2>&1 ; retval=$? &&
-	test $retval -eq 1 &&
-	test_must_fail grep -q Traceback errs
+	(
+		PATH="$TRASH_DIRECTORY/badp4dir:$PATH" &&
+		export PATH &&
+		test_expect_code 1 git p4 clone --dest="$git" //depot >errs 2>&1
+	) &&
+	cat errs &&
+	! test_i18ngrep Traceback errs
 '
 
 test_expect_success 'clone bare' '