Only configure Ceilo DB connection if it is set

The Ceilometer compute agent does not require DB access.
This patch avoids configuring the database/connection setting
if no metadata is present.

Change-Id: I8757019e9731bad91173cbc545ef09d0dbb2e29c
Add iptables rule for nova and mysql

Our testing shows that the following ports need to be
opened in iptables in order for proper behavior when
the firewall is enabled:

1) Mysql port #4444 and #4568 (needed for Galera clustering)
according to Percona documentation at:
http://www.percona.com/doc/percona-xtradb-cluster/5.5/howtos/3nodesec2.html

2) Nova port #8773 for EC2 apis according to Red Hat documentation:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/2/html/Getting_Started_Guide/chap-Deploying_Compute_Services.html

Change-Id: If4f650719828cf8b506cdce21ee8095757844965
Merge "Only configure Ceilo DB connection if it is set"
Merge "Add iptables rule for nova and mysql"