common,iscsi: don't use the shaman search endpoint

common,iscsi: don't use the shaman search endpoint

In commits 39649f0 and bf8cdad we switch from using the shaman /repos endpoint
to the /search endpoint for using the architecture filter.
In fact that filter is also available with the /repos endpoint, which requires
less ansible tasks.

This also adds back a condition remove in 5801171 on the ceph-iscsi
repository and that repository doesn't need to filter on the architecture
because the ceph-iscsi project is noarch.
Both ceph-iscsi and tcmu-runner shaman URLs were using the ceph_dev_branch
and ceph_dev_sha1 variables which doesn't make sense. Those variables are
only useful for the ceph core repository.

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>