test-path-utils: Fix off by one, found by valgrind
test-path-utils: Fix off by one, found by valgrind

When normalizing an absolute path, we might have to add a slash _and_ a
NUL to the buffer, so the buffer was one too small.

Let's just future proof the code and alloc PATH_MAX + 1 bytes.

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git