oeqa/runtime/rpm: Drop log message counting test component

This test is flawed since multiple parts of the system can write to the log
and we obtain different numbers of log messages depending on factors we
can't control.

Drop the log testing component of the test.

[YOCTO #12465]

(From OE-Core rev: fb22cf1891fa8d057348c5270715c45ac3ab9e25)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 2ad815dbafda0b90f5164f05d22dbbc26cb53f13)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>