[FIX] renamed function name db_exist -> exp_db_exist

Fixes problem when trying to restore a database.

See p_christ@hol.gr-20090829152346-7i1iiqs8skdddamq for the function rename

bzr revid: chris.halls@credativ.co.uk-20100409113823-4xuc1bm8zdyfiq32

bin/service/web_services.py

@@ -217,7 +217,7 @@ class db(netsvc.ExportService):
 
         self._set_pg_psw_env_var()
 
-        if self.db_exist(db_name):
+        if self.exp_db_exist(db_name):
             logger.notifyChannel("web-services", netsvc.LOG_WARNING,
                     'RESTORE DB: %s already exists' % (db_name,))
             raise Exception, "Database already exists"