src/poky:rpm: Restore performance in Docker containers

If the maximum number of open file descriptors is much greater than the
usual 1024 (for example inside a Docker container), the performance
drops significantly.

This was reported upstream in:
https://bugzilla.redhat.com/show_bug.cgi?id=1537564
which resulted in:
rpm-software-management/rpm#444

The pull request above has now been integrated and this commit contains
a backport of its three patches, which together change the behavior of
rpm so that its performance is now independent of the maximum number of
open file descriptors.

(From OE-Core rev: 7feed9ccfc4e656c6264f07e13d7e9ef69bdfb06)

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>