tests: enclose $PERL_PATH in double quotes

Otherwise it will be split at a space after "Program" when it is set
to "\\Program Files\perl" or something silly like that.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5551-http-fetch.sh

@@ -130,7 +130,7 @@ test_expect_success EXPENSIVE 'create 50,000 tags in the repo' '
 	done | git fast-import --export-marks=marks &&
 
 	# now assign tags to all the dangling commits we created above
-	tag=$($PERL_PATH -e "print \"bla\" x 30") &&
+	tag=$("$PERL_PATH" -e "print \"bla\" x 30") &&
 	sed -e "s/^:\(.\+\) \(.\+\)$/\2 refs\/tags\/$tag-\1/" <marks >>packed-refs
 	)
 '