ceph-{mon,osd}: move default crush variables

ceph-{mon,osd}: move default crush variables

Since ed36a11 we move the crush rules creation code from the ceph-mon to
the ceph-osd role.
To keep the backward compatibility we kept the possibility to set the
crush variables on the mons side but we didn't move the default values.
As a result, when using crush_rule_config set to true and wanted to use
the default values for crush_rules then the crush rule ansible task
creation will fail.

"msg": "'ansible.vars.hostvars.HostVarsVars object' has no attribute
'crush_rules'"

This patch move the default crush variables from ceph-mon to ceph-osd
role but also use those default values when nothing is defined on the
mons side.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1798864
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>