Standarize ip validation along the code

Details:
 - Use the nova/utils.py validations along the code
 - refactor ipv4 validator to looks like ipv6 validator
 - interprets ip validations exceptions as Invalid IP values

Change-Id: Ia506c00510a066e167d3dcd9dd371a371129a9dd

nova/utils.py

@@ -945,14 +945,16 @@ def is_valid_boolstr(val):
 def is_valid_ipv4(address):
     """Verify that address represents a valid IPv4 address."""
     try:
-        addr = netaddr.IPAddress(address)
-        return addr.version == 4
+        return netaddr.valid_ipv4(address)
     except Exception:
         return False
 
 
 def is_valid_ipv6(address):
-    return netaddr.valid_ipv6(address)
+    try:
+        return netaddr.valid_ipv6(address)
+    except Exception:
+        return False
 
 
 def is_valid_ipv6_cidr(address):