Pull correct docker images for master branch

Enables Policy CSITs for API, PAP, Distribution, Drools-applications,
Apex-PDP and XACML-PDP to pull correct docker images based on the
code branch.

--------------

Updating the policy model json in apex-pdp csit

Changes were made to read the policy model as proper json instead of
json formatted string in APEX-PDP. With this fix in place, the policy
tosca json file need to be updated with the proper json.

Issue-ID: POLICY-1836
Issue-ID: POLICY-1796
Change-Id: I6b99c8ae9cb78dd8ebddc522bc2a7080ec6e5735
Signed-off-by: a.sreekumar <ajith.sreekumar@est.tech>
Signed-off-by: Bilal A <bilal@research.att.com>
diff --git a/scripts/policy/policy-xacml-pdp/docker-compose-pdpx.yml b/scripts/policy/policy-xacml-pdp/docker-compose-pdpx.yml
index 96a4b12..af1cbae 100644
--- a/scripts/policy/policy-xacml-pdp/docker-compose-pdpx.yml
+++ b/scripts/policy/policy-xacml-pdp/docker-compose-pdpx.yml
@@ -21,7 +21,7 @@
     driver: bridge
 services:
    mariadb:
-      image: mariadb:10.2.14
+      image: mariadb:${POLICY_MARIADB_VER}
       container_name: mariadb
       hostname: mariadb
       command: ['--lower-case-table-names=1', '--wait_timeout=28800']
@@ -37,20 +37,20 @@
       ports:
        - "3904:3904"
    pap:
-      image: nexus3.onap.org:10001/onap/policy-pap
+      image: nexus3.onap.org:10001/onap/policy-pap:${POLICY_PAP_VERSION}
       container_name: policy-pap
       depends_on:
        - mariadb
        - message-router
       hostname: policy-pap
    api:
-      image: nexus3.onap.org:10001/onap/policy-api
+      image: nexus3.onap.org:10001/onap/policy-api:${POLICY_API_VERSION}
       container_name: policy-api
       depends_on:
        - mariadb
       hostname: policy-api
    xacml-pdp:
-      image: nexus3.onap.org:10001/onap/policy-xacml-pdp
+      image: nexus3.onap.org:10001/onap/policy-xacml-pdp:${POLICY_XACML_PDP_VERSION}
       container_name: policy-xacml-pdp
       depends_on:
        - mariadb