Fix io.dropwizard.metrics version

Fix io.dropwizard.metrics version

so that it can be removed from odlparent dependencyManagement
in I0ce0e4b7ad54e171c061e1bb91d568b25e9d1145
for https://jira.opendaylight.org/browse/INFRAUTILS-19

see https://lists.opendaylight.org/pipermail/odlparent-dev/2017-November/001460.html

also minor clean up and remove the io.dropwizard.metrics
dependency in sal-distributed-datastore, because that
actually inherits it from sal-clustering-commons anyway.

Change-Id: I74f41742fbcb18bbb9b798b9a4fe73ce5add87eb
Signed-off-by: Michael Vorburger <vorburger@redhat.com>