DnfRepo: fix module_hotfixes keyfile priority level
DnfRepo: fix module_hotfixes keyfile priority level

We were setting the runtime value of the knob instead of the repoconfig
value. This meant that a user wanting to override the config via
`dnf_repo_set_module_hotfixes` (which also sets the runtime value) would
have its changes clobbered.

This should fix Silverblue Rawhide rpm-ostree composes:
https://pagure.io/releng/failed-composes/issue/717
https://pagure.io/releng/failed-composes/issue/929

where we use a hack to allow rpm-ostree to install modular packages
until we fully support modules (which requires #874) and it was getting
reset because `dnf_repo_download_packages` wants to reset the repo
config from the keyfile. For more information, see discussions at:

https://github.com/rpm-software-management/libdnf/pull/885

Closes: #885
Approved by: j-mracek

rpm-software-management/libhif,hughsie/libhif,rpm-software-management/libhif,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libhif,hughsie/libhif,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libdnf,rpm-software-management/libhif,rpm-software-management/libdnf