Improve SAIO deploy document.

improving points:
1. Remove yum install swift in Fedora; Use installing from source for
both Ubuntu and Fedora.
2. Explain you could use all users including root, your own guest. An
d the points developer have to care.

Change-Id: Id6d683441bd790a21734624e29eb7c98bb40de85
Fixes: bug #1126389
Merge "Improve SAIO deploy document."