icinga: have gallium/lanthanum notified to contint

In addition to admins. Borrowed from manifests/role/logging.pp which has
a: $nagios_contact_group = "admins,analytics"

Change-Id: Ib8e9ab5982e8e22427f1ebb09fcd4e52e82d65ee
Merge "icinga: have gallium/lanthanum notified to contint" into production