(gemfile) Relax rspec dependency and add bundler groups
(gemfile) Relax rspec dependency and add bundler groups

This PR relax rspec dependency, for the moment we pin-point to a
specific version.

gwdg/puppet-openstack-cloud,goneri/puppet-openstack-cloud,redhat-cip/puppet-openstack-cloud,gwdg/puppet-openstack-cloud,redhat-cip/puppet-openstack-cloud,goneri/puppet-openstack-cloud,gwdg/puppet-openstack-cloud,Prophidys/puppet-openstack-cloud,Prophidys/puppet-openstack-cloud,redhat-cip/puppet-openstack-cloud,Prophidys/puppet-openstack-cloud,gwdg/puppet-openstack-cloud