Handle over quota exception from Neutron

When using the floating IP in Nova with Neutron, and
a quota limit is exceeded in Neutron, the exception from
the Neutron client results in Nova generating a 500 error.
This is unhelpful to user, and not consistent with nova-networking
Return FloatingIPExceedLimit exception when quota exceeded.

Change I8788993578ac872da9f676fe3e2fb8f98414289d at neutronclient
add OverQuotaClient exception and it is used in this patch

Change-Id: Ieb90521cf231acae8b5a9920acf6c77f2e34ef67
Closes-Bug: #1210598
Closes-Bug: #1301117
Merge "Handle over quota exception from Neutron"