lib/oeqa/selftest/base, scripts/oe-selftest: fix wrong remove path and do a complete...

lib/oeqa/selftest/base, scripts/oe-selftest: fix wrong remove path and do a complete cleanup at the end

The script should clean-up all the .inc files that might
have been created by tests regardless of the outcome or if
the script is interrupted. (currently the
last test will leave a conf/selftest.inc around, even
if it's not included anywhere)
Also fix delete_recipeinc to actually delete what's supposed to.

(From OE-Core rev: 6008745c56800e0f5f01a756be0701cebd9de4ae)

Signed-off-by: Stefan Stanacar <stefanx.stanacar@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>