Description of problem:
currently, ipa-client-install examines only the client's hostname, 
in order to figure out which DNS domain the client belongs in.  
in weird zone/domain setups, though, the client may be configured 
to use a different DNS server than the one that the client's FQDN 
would lead you to expect.  nevertheless, even in these weird DNS
setups, ipa-client-install usually could still run pretty 
automatically, by looking through the client's /etc/resolv.conf
file to search for the right DNS server.  note that the goal here
is for ipa-client-install to do the right setup more often, 
without CLI options, and without throwing any warning messages or
prompts to the user for easily-mistyped names.

note that the proposal here is not to replace i-c-i's current
analysis of the client's FQDN.  rather, the proposal would
supplement that search, after the FQDN parsing fails to yield
a successful DNS lookup.

FWIW, i'm filing this RFE at simo's suggestion, after he, edewata,
and sgallagh helped me through my confusing newbie experience while
setting up ipa-client in just such a messed-up DNS config (my own).

Version-Release number of selected component (if applicable): 1.2.1

How reproducible:  yes, reliable

Steps to Reproduce:
1. change a desktop's FQDN, so that the donmain-suffix doesn't match
   the host's actual DNS domain.
2. set up the DNS server's .rev file to list the new hostname correctly
3. run ipa-client-install, without CLI options.
  
Actual results:   i-c-i throws a warning:  "Discovery of DNS failed!"

Expected results: i-c-i should say, "Discovery of DNS succeeded," or
                  whatever i-c-i sings for its happy song.

Additional info: