cleanup notifier default variables

playbooks/edx-east/notifier.yml

+- name: Configure notifier instance
+  hosts: all
+  sudo: True
+  gather_facts: True
+  roles:
+    - role: aws
+      when: COMMON_AWS_SYNC
+    - notifier
+

playbooks/roles/notifier/defaults/main.yml

@@ -8,7 +8,6 @@ NOTIFIER_DB_DIR: "{{ NOTIFIER_HOME }}/db"
 NOTIFIER_SOURCE_REPO: "https://github.com/edx/notifier.git"
 NOTIFIER_CODE_DIR: "{{ NOTIFIER_HOME }}/src"
 NOTIFIER_VERSION: "master"
-NOTIFIER_GIT_IDENTITY_PATH: "{{ secure_dir }}/files/git-identity"
 NOTIFIER_REQUIREMENTS_FILE: "{{ NOTIFIER_CODE_DIR }}/requirements.txt"
 NOTIFIER_LOG_LEVEL: "INFO"
 NOTIFIER_RSYSLOG_ENABLED: "yes"
@@ -89,7 +88,7 @@ notifier_env_vars:
   CS_API_KEY: "{{ NOTIFIER_COMMENT_SERVICE_API_KEY }}"
   US_URL_BASE: "{{ NOTIFIER_USER_SERVICE_BASE }}"
   US_API_KEY: "{{ NOTIFIER_USER_SERVICE_API_KEY }}"
-  DATADOG_API_KEY: "{{ DATADOG_API_KEY }}"
+  DATADOG_API_KEY: "{{ DATADOG_API_KEY|default('') }}"
   LOG_LEVEL: "{{ NOTIFIER_LOG_LEVEL }}"
   RSYSLOG_ENABLED: "{{ NOTIFIER_RSYSLOG_ENABLED }}"
   BROKER_URL: "{{ NOTIFIER_CELERY_BROKER_URL }}"