Check fixed-cidr is within fixed-range-v4

Creating a network using 'nova network-create' allows the
creation of fixed IPs that fall outside the fixed-range-v4,
resulting in invalid fixed IPs. The following patch add a
check to see if the fixed-cidr subnet is within the
fixed-range-v4 and throws an exception if it does not.

Change-Id: I00458b54094d3371da63d22e3356660194e2fb95
Closes-Bug: #1367060
Merge "Check fixed-cidr is within fixed-range-v4"