No longer link pip to pip-python on Red Hat

* modules/pip/manifests/init.pp: Remove the symlink workaround for
older python-pip EPEL packages since current versions now provide
/usr/bin/pip directly instead of /usr/bin/pip-python. The latter has
been switched to a symlink itself, so without this change in Puppet
we get circular symlinks and no executable.

Change-Id: If09a9c2a511dcc9ae845833543e304f1459fdeb2