Clearer comments in defaults

Author: Lionel Sausin (Numérigraphe)

defaults/main.yml

@@ -628,11 +628,11 @@ postgresql_restart_after_crash: on
 #------------------------------------------------------------------------------
 # Should we run pgtune and accept the changes it proposes?
 postgresql_pgtune: no
-# Total system memory, will attempt to detect if set to "no"
+# Total system memory in bytes, will attempt to detect if set to "no"
 postgresql_pgtune_memory: no
 # Database type, valid options are DW, OLTP, Web, Mixed, Desktop
 postgresql_pgtune_type: Mixed
-# Maximum number of expected connections, default depends on database type
+# Maximum number of expected connections, if "no", default based on db type
 postgresql_pgtune_connections: no