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]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 2ad815db)
Signed-off-by: Steve Sakoman <steve@sakoman.com>