packagers: yum: disable self if not active

this breaks offline packager if exists, introduced at:
2b4f0bdccf9 since 2013-16-07, not sure how it passed all QA cycles.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1112370
Change-Id: I2ddd0ac38828bc0536026df465fc17557ac20ce7
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>