package_manager.py: enable dnf's repo_gpgcheck if feed signing is enabled
If package feed signing is enabled enable repo gpg signature check for
rpm repositories added via PACKAGE_FEED_URIS. This has the implication
that all repositories added via this mechanism must be signed with the
same key.
[YOCTO #11209]
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
