Use Go-template placeholders and shell-guarded CREATE DATABASE

- Telegraf's outputs.postgresql plugin uses Go text/template syntax,
  not uppercase tokens. The {TABLE}/{COLUMNS}/{TABLELITERAL} strings
  were passed through to Postgres literally, producing syntax errors
  on every metric's first write. Switch to {{ .table }}, {{ .columns }},
  and {{ .table|quoteLiteral }} so partitioned parents and the partman
  create_parent() call succeed.
- Replace the \gexec "CREATE DATABASE ... WHERE NOT EXISTS" idiom in
  both init-users.sh and telegraf_users.sls with an explicit shell
  conditional. The prior idiom occasionally fired CREATE DATABASE even
  when so_telegraf already existed, producing duplicate-key failures.

salt/postgres/files/init-users.sh

@@ -20,7 +20,6 @@ EOSQL
 # Bootstrap the Telegraf metrics database. Per-minion roles + schemas are
 # reconciled on every state.apply by postgres/telegraf_users.sls; this block
 # only ensures the shared database exists on first initialization.
-psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
-    SELECT 'CREATE DATABASE so_telegraf'
-    WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'so_telegraf')\gexec
-EOSQL
+if ! psql -U "$POSTGRES_USER" -tAc "SELECT 1 FROM pg_database WHERE datname='so_telegraf'" | grep -q 1; then
+    psql -v ON_ERROR_STOP=1 -U "$POSTGRES_USER" -c "CREATE DATABASE so_telegraf"
+fi

salt/postgres/telegraf_users.sls

@@ -34,10 +34,9 @@ postgres_wait_ready:
 postgres_create_telegraf_db:
   cmd.run:
     - name: |
-        docker exec -i so-postgres psql -v ON_ERROR_STOP=1 -U postgres -d postgres <<'EOSQL'
-        SELECT 'CREATE DATABASE so_telegraf'
-        WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'so_telegraf')\gexec
-        EOSQL
+        if ! docker exec so-postgres psql -U postgres -tAc "SELECT 1 FROM pg_database WHERE datname='so_telegraf'" | grep -q 1; then
+          docker exec so-postgres psql -v ON_ERROR_STOP=1 -U postgres -c "CREATE DATABASE so_telegraf"
+        fi
     - require:
       - cmd: postgres_wait_ready