rpm: put numpy and scipy deps in distro conditionals

rpm: put numpy and scipy deps in distro conditionals

Without this patch, attempts to install the ceph-mgr-diskprediction-local RPM
fail on SUSE platforms with the following error:

can't install ceph-mgr-diskprediction-local-14.1.0.402+ga396e8bf3b-3742.1.noarch:
  nothing provides numpy needed by ceph-mgr-diskprediction-local-14.1.0.402+ga396e8bf3b-3742.1.noarch
  nothing provides scipy needed by ceph-mgr-diskprediction-local-14.1.0.402+ga396e8bf3b-3742.1.noarch

Also take into account package naming differences between Fedora and
RHEL/CentOS.

Signed-off-by: Kefu Chai <kchai@redhat.com>
Signed-off-by: Nathan Cutler <ncutler@suse.com>