monitor: fixed default value of 'user' config option

1) man page explicitly and unconditionally says that default value
for this option is 'root' so this patch just aligns code with a doc

2) since at the moment "sssd running as non-root" feature isn't really
tested and is proposed at "use at your own risk" basis it wouldn't hurt
to require user to configure this option explicitly even when sssd is
built with "--with-sssd-user=sssd"

This should be changed when feature is really supported.

:relnote: default value of 'user' config option was fixed into accordance
with man page, i.e. default is 'root'

Reviewed-by: Sumit Bose <[email protected]>

src/monitor/monitor.c

@@ -905,7 +905,7 @@ static int get_service_user(struct mt_ctx *ctx)
 
     ret = confdb_get_string(ctx->cdb, ctx, CONFDB_MONITOR_CONF_ENTRY,
                             CONFDB_MONITOR_USER_RUNAS,
-                            SSSD_USER, &user_str);
+                            "root", &user_str);
     if (ret != EOK) {
         DEBUG(SSSDBG_FATAL_FAILURE, "Failed to get the user to run as\n");
         return ret;