openshift.ks: Add CONF_ACTIVEMQ_REPLICANTS

Add the CONF_ACTIVEMQ_REPLICANTS setting, which specifies a comma-separated
list of hostnames for ActiveMQ broker replicants.  This setting defaults
the value of CONF_ACTIVEMQ_HOSTNAME.

Add the CONF_ACTIVEMQ_AMQ_USER_PASSWORD setting, which specifies the
password to use for ActiveMQ's "amq" user (see below).

Modify configure_activemq so that if a list of replicants is specified
where that list includes hostnames other than the hostname of the host that
is currently being configured, configure_activemq will add appropriate
networkConnector entries to activemq.xml, add an "amq" user with the
password specified by the CONF_ACTIVEMQ_AMQ_USER_PASSWORD setting, and open
port 61616 (which replicants use to communicate using the OpenWire
protocol).  Also modify the policyEntries configuration to match Puppet
Labs' recommendations.

Add a new function generate_mcollective_pools_configuration, which
outputs the plugin.activemq.pool.* settings for the MCollective
configuration files using the new CONF_ACTIVEMQ_REPLICANTS setting.

Use this new generate_mcollective_pools_configuration function in
configure_mcollective_for_activemq_on_broker and
configure_mcollective_for_activemq_on_node so that a new broker or node
host is configured to use whatever replicants are specified by
CONF_ACTIVEMQ_REPLICANTS.