Correct developer mode package var name

In https://review.openstack.org/363077 the var name was incorrectly
set to keystone_developer_distro_packages instead of
keystone_developer_mode_distro_packages as has been the pattern
used across all the other roles. This patch corrects the var name
to ensure that it fits the same pattern as all other roles.

Change-Id: Ia2d3b14b6d3fcf86bdc53a901f1ef2aa6e8128bd

tasks/keystone_install_apt.yml

@@ -90,6 +90,6 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  with_items: "{{ keystone_developer_distro_packages }}"
+  with_items: "{{ keystone_developer_mode_distro_packages }}"
   when:
     - keystone_developer_mode | bool

tasks/keystone_install_yum.yml

@@ -125,6 +125,6 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  with_items: "{{ keystone_developer_distro_packages }}"
+  with_items: "{{ keystone_developer_mode_distro_packages }}"
   when:
     - keystone_developer_mode | bool

vars/redhat-7.yml

@@ -51,7 +51,7 @@ keystone_idp_distro_packages:
 keystone_sp_distro_packages:
   - shibboleth
 
-keystone_developer_distro_packages:
+keystone_developer_mode_distro_packages:
   - '@Development Tools'
 
 keystone_apache_default_sites:

vars/ubuntu-14.04.yml

@@ -44,7 +44,7 @@ keystone_idp_distro_packages:
 keystone_sp_distro_packages:
   - libapache2-mod-shib2
 
-keystone_developer_distro_packages:
+keystone_developer_mode_distro_packages:
   - build-essential
 
 keystone_apache_default_sites:

vars/ubuntu-16.04.yml

@@ -44,7 +44,7 @@ keystone_idp_distro_packages:
 keystone_sp_distro_packages:
   - libapache2-mod-shib2
 
-keystone_developer_distro_packages:
+keystone_developer_mode_distro_packages:
   - build-essential
 
 keystone_apache_default_sites: