881847 - allow system group names with spaces and other characters

pulpv2 does not support spaces and other non alpha-numeric
characters in the id, so in order to create a group in katello
with those characters we just need to labelize the name when
constructing the pulpId
Merge pull request #1401 from jlsherrill/pulpv2-group_pulp_id

881847 - allow system group names with spaces and other characters