shared policy shouldn't have unshared rules

A shared firewall policy should always have shared rules. So the following
cases should not be allowed:
1.Create shared policy with unshared rules
2.Update policy shared=True when it has unshared rules
3.Update policy with shared=True and unshared rules
4.Update shared policy with unshared rules

Change-Id: I3d71899c328d3fefa96c1f99d6ba706160e445cc
Closes-bug: 1334981
Merge "shared policy shouldn't have unshared rules"