Show error message for invalid IPs in client install

Re-raise the thrown exception to get an error message
instead of a traceback during ipa-client-install with
invalid IP address.

https://fedorahosted.org/freeipa/ticket/6340

Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

ipapython/ipautil.py

@@ -133,8 +133,11 @@ class CheckedIPAddress(UnsafeIPAddress):
     """
     def __init__(self, addr, match_local=False, parse_netmask=True,
                  allow_loopback=False, allow_multicast=False):
-
+        try:
             super(CheckedIPAddress, self).__init__(addr)
+        except netaddr.core.AddrFormatError as e:
+            raise ValueError(e)
+
         if isinstance(addr, CheckedIPAddress):
             self.prefixlen = addr.prefixlen
             return