oeqa/selftest/bbtests: Update message lookup for test_git_unpack_nonetwork_fail

bitbake's output changed, update the test

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 7e64b63f)
Signed-off-by: Steve Sakoman <steve@sakoman.com>