Description of problem:
I entered in an invalid IP for for the DNS nameserver's IP and then the rest I entered good information:

   Enter the DNS nameserver's IP address to use for the Overcloud: 192.168.175.300

It went ahead and did all kinds of installation steps probably taking about five minutes before it tried to use the DNS server's address, and finally failed.

It would be better if it validated this information as it was entered.


Version-Release number of selected component (if applicable):
QCIOOO-8.0-RHEL-7-20160708.t.1

How reproducible:
Everytime

Steps to Reproduce:
1.  When you get to the undercloud installer enter an invalid DNS IP.
2.  Enter the rest of the information correctly.

Actual results:

Will do much of the installation only to eventually fail:

  Invalid input for dns_nameservers.  Reason: '192.168.175.300' is not a valid
  server.  '192.168.175.300's is not a valid IP address.



Expected results:

Fail early due to the invalid IP.