Add db2 support to neutron on redhat platform

Add a new attribute
default["openstack"]["network"]["platform"]["db2_python_packages"]
and add install DB python packages block in common recipe

Change-Id: If38891ba734f0ba67b413175ddc9bde351248a46
Implements: blueprint db2-support
Correct neutron related package/service names on redhat platform

Some package and service names were wrong in attribute file,
so I corrected them in order to install and start them successfully.

Change-Id: Iec35a9fe67accd50f3b8074b205951f58032736a
Closes-bug: 1256377
Merge "Correct neutron related package/service names on redhat platform"