task/hadoop: fix for multi cluster is_type() change

task/hadoop: fix for multi cluster is_type() change

This is the only non-ceph task that uses custom roles, and it happens
to put a '.' as a delimiter between hadoop and the rest of the
role. Since the multi-cluster branch, is_type() is ceph-specific and
interprets this as a cluster named hadoop.

To avoid needing to change several branches in ceph-qa-suite, just use
a local is_hadoop_type() function instead of relying on the now
ceph-specific misc.is_type().

Fixes: http://tracker.ceph.com/issues/15862
Signed-off-by: Josh Durgin <jdurgin@redhat.com>