Allow the test suite to pass in a directory whose name contains spaces

Allow the test suite to pass in a directory whose name contains spaces

It is totally legitimate to clone Git's source code anywhere, including
into, say, directories whose name (or the name of its absolute path)
contains spaces.

However, a couple of tests failed to anticipate this, for lack of
quoting (or in one instance, for failure to expect more than one space
in the absolute path of the TEST_DIRECTORY). This can be easily verified
by calling these commands in your current clone:

	git clone . with\ spaces
	cd with\ spaces
	make -j15 test

Let's fix this.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>