Description of problem:
When I try to add punycode-encoded IDN name into FreeIPA managed DNS, I get following error:

#v+
Record name: xn--dogstaff-33b
>>> Record name: only letters, numbers, _, and - are allowed. DNS label may not start or end with -
#v-

looks like regex in util.py:validate_dns_label() is too restrictive.

Version-Release number of selected component (if applicable):
freeipa-python-3.3.0-2.fc19.x86_64

How reproducible:
Always.