ci: Makefile: Expose the CI_USER_LOGIN variable for users to use
ci: Makefile: Expose the CI_USER_LOGIN variable for users to use

More often than not I find myself debugging in the containers which
means that I need to have root inside, but without manually tweaking
the Makefile each time the execution would simply fail thanks to the
uid/gid mapping we do. What if we expose the CI_USER_LOGIN variable, so
that when needed, the root can be simply passed with this variable and
voila - you have a root shell inside the container with CWD=~root.

Signed-off-by: Erik Skultety <2c14d38fa47c8799f1b9c16280abe27f8edfec6e@redhat.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

libvirt/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,libvirt/libvirt,olafhering/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,zippy2/libvirt,olafhering/libvirt,jfehlig/libvirt,zippy2/libvirt,nertpinx/libvirt,crobinso/libvirt,olafhering/libvirt,crobinso/libvirt