build/ops: rpm: recommend python-influxdb with ceph-mgr

build/ops: rpm: recommend python-influxdb with ceph-mgr

The influxdb module won't run if python-influxdb is not present (but it will be
graceful about not running). That means python-influxdb is a dependency of
that module, not mgr itself. However, we are not (yet) packaging the modules
separately. (When we do, this could become a Requires: of the module.)

RPM itself does not support "Recommends", and ignores this line. Higher-level
tools may or may not support it, so put this line in a SUSE-only conditional
since we know that zypper supports it.

Signed-off-by: Nathan Cutler <ncutler@suse.com>
Signed-off-by: Tim Serong <tserong@suse.com>