Enable bcfg2-yum-helper to depsolve for arches incompatible with server

By default, the yum dependency resolver uses the host's architecture
to filter compatible packages.  This prevents dependency resolution
when the bcfg2 client's architecture is incompatible with the
server's.

This workaround checks the <Arch/> element for each of the client's yum
sources, and if they are all identical, passes that architecture to
bcfg2-yum-helper to override the default.

The rpmUtils.arch module may only be configured for a single
architecture.  If multiple architectures are configured in yum
sources, we don't know which one to pick, so use the default behavior
instead.
Merge pull request #164 from zultron/maint

Enable bcfg2-yum-helper to depsolve for arches incompatible with server
misc/bcfg2.spec Remove duplicate checks for systemd in RPM scriptlets

In the RPM scriptlets, there's first a check for fedora 18 or greater,
then if that's not true, a check for fedora 16 or greater.  Due to
some bug in how nested %if statements work in RPM scriptlets, the
second test is evaluating true even on non-Fedora systems, which is
leading to systemd commands being put in RHEL6 RPM scriptlets.

This change removes the second check.  If there needed to be a check
for versions of Fedora 16 and 17, they will no longer work, but since
neither of those are supported versions of Fedora, I suspect we don't
need to include logic for them.
misc/bcfg2.spec: Remove second, unnecessary %endif
misc/bcfg2.spec: Bumped release and added a changelog entry