btrfs-progs: tests: fix TEST_LOG=dump in convert tests

Test failure in convert tests with log dump does not happen because
_fail is called before that and exits. Other test types are ok.

Signed-off-by: David Sterba <dsterba@suse.com>

tests/convert-tests.sh

@@ -40,10 +40,10 @@ run_one_test() {
 		# Only support custom test scripts
 		./test.sh
 		if [ $? -ne 0 ]; then
-			_fail "test failed for case $testname"
 			if [[ $TEST_LOG =~ dump ]]; then
 				cat "$RESULTS"
 			fi
+			_fail "test failed for case $testname"
 		fi
 	else
 		_fail "custom test script not found"