Add note regarding local port range

It is possible for the default port of a service (in particular,
keystone's administrative endpoint) to fall within a host's local
port range. This patch reminds users of this, and adds instructions
on how to:

- check a host's' port range
- check whether a port is already in use

Change-Id: If57d186153b4ffb8367d685a09675880b4fdaa04
Partial-Bug: #1261617
Fix wrong link to Configure Migrations

The "Configure migrations" section doesn't exist anymore in the icehouse
configuration reference, but in the cloud administrator guide.

Change-Id: Ia6f73ea961249f8536958ea757ac6a08f66e1606
Closes-Bug: #1327691
Fix the typo in volume read-only access cli command

The command to set a volume to read-only access has a typo
in the user guide. The command listed in the guide is
cinder read-only-mode-update VOLUME BOOLEAN
but the correct command is
cinder readonly-mode-update VOLUME BOOLEAN

Change-Id: I60eae0fd67faa153b92def69dd5b567738e9dcbb

Closes-Bug: #1328282

Change-Id: I60eae0fd67faa153b92def69dd5b567738e9dcbb
Merge "Add note regarding local port range"
Merge "Fix wrong link to Configure Migrations"
Merge "Fix the typo in volume read-only access cli command"