Adding the dependency on nc in foreman_client.sh

puppet agent --test ends up calling "python
/var/lib/puppet/lib/facter/netns.py" which complains if nc is not
installed.  So, let's add that dependency.  I'm also hoping this
addition will prevent hangs in foreman_client.sh (I found this issue
investigating a hang).
Merge pull request #11 from cwolferh/add_dep_on_nc

Adding the dependency on nc in foreman_client.sh