Fix some Markdown formatting issues

Address miscellaneous issues with Markdown formatting in comments which
are consumed by shocco when generating the online documentation.

Change-Id: I953075cdbddbf1f119c6c7e35f039e2e54b79078

lib/databases/mysql

@@ -2,7 +2,8 @@
 # Functions to control the configuration and operation of the **MySQL** database backend
 
 # Dependencies:
-# DATABASE_{HOST,USER,PASSWORD} must be defined
+#
+# - DATABASE_{HOST,USER,PASSWORD} must be defined
 
 # Save trace setting
 MY_XTRACE=$(set +o | grep xtrace)

lib/databases/postgresql

@@ -2,7 +2,8 @@
 # Functions to control the configuration and operation of the **PostgreSQL** database backend
 
 # Dependencies:
-# DATABASE_{HOST,USER,PASSWORD} must be defined
+#
+# - DATABASE_{HOST,USER,PASSWORD} must be defined
 
 # Save trace setting
 PG_XTRACE=$(set +o | grep xtrace)