Remove unnecessary package installs

Xenial PIP installs do not need all of the extra packages laid
down on the host for SNI support like Trusty did.

Change-Id: Ia3fe82b78ef06d8b8d90eb5071bf0e284dba38b9

defaults/main.yml

@@ -35,14 +35,14 @@ pip_source_install_options: ""
 # The URL/path of a constraints file to use when installing the additional pip packages.
 #pip_install_upper_constraints: "http://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt"
 
+pip_install_distro_packages: []
+
 # This list var can be used to specify specific versions of pip, setuptools,
 # wheel and any other packages which must be installed when pip installs.
 pip_packages:
   - pip
 
-pip_required_pip_packages:
-  - ndg-httpsclient # SSL SNI support
-  - requests # SSL SNI support
+pip_required_pip_packages: []
 
 ## APT Cache options
 cache_timeout: 600

vars/redhat-7.yml

@@ -20,3 +20,7 @@ pip_install_distro_packages:
   - python-devel
   - python-pyasn1
   - pyOpenSSL
+
+pip_required_pip_packages:
+  - ndg-httpsclient # SSL SNI support
+  - requests # SSL SNI support

vars/ubuntu-14.04.yml

@@ -21,3 +21,7 @@ pip_install_distro_packages:
   - python-dev
   - python-openssl
   - python-pyasn1
+
+pip_required_pip_packages:
+  - ndg-httpsclient # SSL SNI support
+  - requests # SSL SNI support

vars/ubuntu-16.04.yml

@@ -12,13 +12,3 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-pip_install_distro_packages:
-  - build-essential
-  - python-dev
-  - python-setuptools
-  - libffi-dev
-  - libssl-dev
-  - python-dev
-  - python-openssl
-  - python-pyasn1