Fix PostgreSQL images failing to start in CI

PostgreSQL 9.6.17 was released recently and now requires a password to
be set. We can also set the `POSTGRES_HOST_AUTH_METHOD` to `trust` to
bypass a password. Since this is just running in CI, this should be
acceptable.

Closes https://gitlab.com/gitlab-org/gitlab/issues/205820

.gitlab/ci/global.gitlab-ci.yml

@@ -203,6 +203,8 @@
     - name: postgres:9.6
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
+  variables:
+    POSTGRES_HOST_AUTH_METHOD: trust
 
 .use-pg10:
   image: "registry.gitlab.com/gitlab-org/gitlab-build-images:ruby-2.6.5-golang-1.12-git-2.24-lfs-2.9-chrome-73.0-node-12.x-yarn-1.21-postgresql-10-graphicsmagick-1.3.34"
@@ -210,6 +212,8 @@
     - name: postgres:10.9
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
+  variables:
+    POSTGRES_HOST_AUTH_METHOD: trust
 
 .use-pg9-ee:
   services:
@@ -217,6 +221,8 @@
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
     - name: elasticsearch:6.4.2
+  variables:
+    POSTGRES_HOST_AUTH_METHOD: trust
 
 .use-pg10-ee:
   image: "registry.gitlab.com/gitlab-org/gitlab-build-images:ruby-2.6.5-golang-1.12-git-2.24-lfs-2.9-chrome-73.0-node-12.x-yarn-1.21-postgresql-10-graphicsmagick-1.3.34"
@@ -225,6 +231,8 @@
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
     - name: elasticsearch:6.4.2
+  variables:
+    POSTGRES_HOST_AUTH_METHOD: trust
 
 .only-ee:
   only: