database: fix PostgreSQL connection string

If all databases drivers are loaded, MySQL SQLAlchemy driver
overrides all the other one that might not have set one.
This patches fixes that.

Change-Id: If6d8d08e5b7b7c48ca012677b536d71058def6fd
Closes-Bug: #1493304

lib/databases/mysql

@@ -12,12 +12,6 @@ MY_XTRACE=$(set +o | grep xtrace)
 set +o xtrace
 
 MYSQL_DRIVER=${MYSQL_DRIVER:-PyMySQL}
-# Force over to pymysql driver by default if we are using it.
-if is_service_enabled mysql; then
-    if [[ "$MYSQL_DRIVER" == "PyMySQL" ]]; then
-        SQLALCHEMY_DATABASE_DRIVER=${SQLALCHEMY_DATABASE_DRIVER:-"pymysql"}
-    fi
-fi
 
 register_database mysql
 
@@ -30,6 +24,14 @@ fi
 # Functions
 # ---------
 
+function get_database_type_mysql {
+    if [[ "$MYSQL_DRIVER" == "PyMySQL" ]]; then
+        echo mysql+pymysql
+    else
+        echo mysql
+    fi
+}
+
 # Get rid of everything enough to cleanly change database backends
 function cleanup_database_mysql {
     stop_service $MYSQL

lib/databases/postgresql

@@ -21,6 +21,10 @@ register_database postgresql
 # Functions
 # ---------
 
+function get_database_type_postgresql {
+    echo postgresql
+}
+
 # Get rid of everything enough to cleanly change database backends
 function cleanup_database_postgresql {
     stop_service postgresql