Fix proxy usage for docker external

The process that retrieves Docker images hosted externally was
missing a step in its configuration. This change fix the
configuration and unblock the pending Unit Tests.

Change-Id: I5a6b39086eb806bab5bb2667092a154e230d33ef
Signed-off-by: Victor Morales <victor.morales@intel.com>
Issue-ID: INT-227
diff --git a/bootstrap/vagrant-onap/lib/_onap_functions b/bootstrap/vagrant-onap/lib/_onap_functions
index 18a4659..cedd6f0 100755
--- a/bootstrap/vagrant-onap/lib/_onap_functions
+++ b/bootstrap/vagrant-onap/lib/_onap_functions
@@ -12,7 +12,6 @@
     echo $docker_version > /opt/config/docker_version.txt
 }
 
-# TODO(electrocucaracha): Determine how to use this behind a proxy
 # docker_openecomp_login() - Login to OpenECOMP Docker Hub
 function docker_openecomp_login {
     install_docker
@@ -24,7 +23,7 @@
     local image=$1
     local tag=$2
     docker_openecomp_login
-    pull_docker_image $nexus_docker_repo/openecomp/${image}:$docker_version $tag
+    pull_docker_image $nexus_docker_repo/openecomp/${image}:${docker_version-latest} $tag
     docker logout
 }
 
@@ -33,7 +32,7 @@
     local image=$1
     local tag=$2
     docker_openecomp_login
-    pull_docker_image $nexus_docker_repo/onap/${image}:$docker_version $tag
+    pull_docker_image $nexus_docker_repo/onap/${image}:${docker_version-latest} $tag
     docker logout
 }