packaging: engine-setup - Don't change selinux context in runtime

Engine setup use miniyum to perform RPM/YUM based operations, and asks
miniyum to change the selinux context of the whole proccess during it's
intializtion.
This patch removes the selinux context change, as it blocks dbus
messeges issued by firewalld api, and currently not really needed.

Change-Id: I46e04f185c04cc30c8e0b52367d6209716dc0d98
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=904153
Signed-off-by: Ofer Schreiber <oschreib@redhat.com>