centos: we install 'hostname' in base image

There is no need to install it in other images.

Change-Id: I9fdb987533662ee532141b06fc23b64c92788429

docker/keepalived/Dockerfile.j2

@@ -9,7 +9,6 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
 
 {% if base_package_type == 'rpm' %}
     {% set keepalived_packages = [
-        'hostname',
         'keepalived'
     ] %}
 {% elif base_package_type == 'deb' %}

docker/mariadb/mariadb-server/Dockerfile.j2

@@ -15,7 +15,6 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
 {% if base_package_type == 'rpm' %}
     {% set mariadb_packages = [
         'expect',
-        'hostname',
         'mariadb-backup',
         'mariadb-server',
         'pv',

docker/rabbitmq/Dockerfile.j2

@@ -21,7 +21,6 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
 
     {% set rabbitmq_packages = [
         'erlang-25.*',
-        'hostname',
         'rabbitmq-server-3.10.*'
     ] %}