dashboard: Resolve FQDN / hostname mismatch in hosts overview panel

dashboard: Resolve FQDN / hostname mismatch in hosts overview panel

In the AVG Disk Utilization panel, the result is calculated
by combining the output of node_disk_io_time_seconds_total
with the output of ceph_disk_occupation. However, the
first vector encodes the instance label with the full FQDN
while the ceph label only contains the hostname:port. In
order for these to match correctly, the domain name and port
has to be stripped from the labels.

Fixes: https://tracker.ceph.com/issues/44784
Signed-off-by: Kristoffer Grönlund <kgronlund@suse.com>