ceph-common: install nfs-ganesha FSALs on Debian

ceph-common: install nfs-ganesha FSALs on Debian

Prior to this change, ceph-ansible would install the main NFS Ganesha
server daemon on Ubuntu, but it would skip the Ceph FSALs.

Running "apt-get install nfs-ganesha" will only install the main NFS Ganesha
server. It does *not* pull in the RGW FSAL
(/usr/lib/x86_64-linux-gnu/ganesha/libfsalrgw.so)

Running "apt-get install nfs-ganesha-fsal" will install the RGW FSAL as
well as the main NFS Ganesha server package.

Signed-off-by: Ken Dreyer <kdreyer@redhat.com>