client install: correctly report all failures
In commit 5249eb817efbb5708d097173a8d5f1e322fb201e, the client install code
was converted to use exception handling instead of return codes. However,
some return statements were not converted to raise statements and as a
result, ipa-client-install will report success in some error conditions.
Convert the return statements to raise statements to fix the issue.
https://fedorahosted.org/freeipa/ticket/6392
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>