Install Guide: Remove duplicate sentences

The text for mysql_secure_installation was shown for os="opensuse;sles"
since it was on both paragraphs. Once is enough ;)

Change-Id: I1ffaa7faac55379d8bd78753aeff6e1f7e834519
Closes-Bug: 1245950
backport: havana
(cherry picked from commit 0e15e2310d4a08b4b83fc76be42d3155cded4656)
Install Guide: Fix nova.conf for nova-network

These fixes are needed for Ubuntu and openSUSE/SLES:
Setup nova.conf properly
Start libvirtd (openSUSE/SLES)

Change-Id: Ied6580fbbde85bf86e8d1986dc5e94e7a54b27d7
backport: havana
Closes-Bug: 1245846
Closes-Bug: 1245869
(cherry picked from commit 824a40cda54d6af51bd6a57dce983922ef1d9659)
Merge "Install Guide: Remove duplicate sentences" into stable/havana