Configure ironic services to be automatically started at boot time in 'install guide'

[Wang Wei]

In Fedora/RHEL7/CentOS7, when ironic was installed,the services (openstack-ironic-api, openstack-ironic-conductor) are neither active nor configured as started automatically at boot time.
And there has no such problem in Ubuntu.

In this case, after installed, we need to use commands 'systemctl start xxx' and
'systemctl enable xxx' to start and enable those services in Fedora/RHEL7/CentOS7.

So, in 'Bare Metal service Installation Guide',
we should change the install section as follow:

Before changed
---------------------
Install from packages:

 Ubuntu 14.04 (trusty) or higher:
    apt-get install ironic-api ironic-conductor python-ironicclient

 RHEL7/CentOS7/Fedora 21 or higher:
   yum install openstack-ironic-api openstack-ironic-conductor python-ironicclient

After changed
 ---------------------
Install from packages and configure services:

 Ubuntu 14.04 (trusty) or higher:
   sudo apt-get install ironic-api ironic-conductor python-ironicclient

 RHEL7/CentOS7/Fedora 21 or higher:
   sudo yum install openstack-ironic-api openstack-ironic-conductor python-ironicclient
   sudo systemctl enable openstack-ironic-api openstack-ironic-conductor
   sudo systemctl start openstack-ironic-api openstack-ironic-conductor

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/222920

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/222920
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=7ebe6437464e99faf5b6d5e8ace635121cc72d7c
Submitter: Jenkins
Branch: master

commit 7ebe6437464e99faf5b6d5e8ace635121cc72d7c
Author: Wang Wei <email address hidden>
Date: Sun Sep 13 22:26:01 2015 +0800

    Update 'Installation Guide' for RHEL7/CentOS7/Fedora

    Change-Id: I3c2b0f942d0148efa046cff7c6b34695851b8f8a
    Closes-Bug: #1495241