Don't ignore return values from the git command lines. If something goes
wrong, fail the test right away.
(From OE-Core rev: dfc178a70d6fa60e89d4716f05d68e2c72c6ecd3)
Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>