oe-selftest: add a test for failing package post-installation scriptlets
The test runs a scriptlet that has an intentionally failing command in the middle
and checks for two things:
1) that bitbake does warn the user about the failure
2) that scriptlet execution stops at that point.
The test is run for all three package types: rpm, deb, ipk.
Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
