Adding the possibility to skip checks on rpmbuild

This way you can build the rpms skipping the tests just defining the variable
with_check to 0 when running rpmbuild, also skipping checks by default when
building on el* based hosts

Change-Id: I674ae8f8e5ff8b21a0175197bd42e61af6075afd
Signed-off-by: David Caro <dcaroest@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29213
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>