Instruction for multi node setup misses /var/run/swift creation

Multiple Server Swift Installation (Ubuntu) instruction does not
indicate that the directory /var/run/swift needs to be created.
That directory actually needs to be created and the ownship needs
to be changed to the user/group which swift service runs under.

This patch will fix the document and gives the steps how to create
the directory and set the ownership right. It also gives instruction
on how the script can be added so that swift services can be resarted
after system reboots.

Change-Id: Id61aa67cc0d6f66d749701e6ea824b1ff3b2c478
Fixes: bug #1156631
Merge "Instruction for multi node setup misses /var/run/swift creation"