mod_asis: Fix the log level of the message AH01236

Change the log level from ERROR to DEBUG.

The message \"mod_asis: ap_pass_brigade failed for file ...\" was logged with
the level ERROR. This log level is inappropriate here, because a client can
trigger this log message by aborting the request.

Most other modules don't log at all or use the log level DEBUG when
ap_pass_brigade() fails.

Submitted by: Michael Kaufmann <mail michael-kaufmann.ch>
Github: closes #527


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1924954 13f79535-47bb-0310-9956-ffa450edef68

Author: notroj

modules/generators/mod_asis.c

@@ -99,7 +99,7 @@ static int asis_handler(request_rec *r)
         APR_BRIGADE_INSERT_TAIL(bb, b);
         rv = ap_pass_brigade(r->output_filters, bb);
         if (rv != APR_SUCCESS) {
-            ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01236)
+            ap_log_rerror(APLOG_MARK, APLOG_DEBUG, rv, r, APLOGNO(01236)
                           "mod_asis: ap_pass_brigade failed for file %s", r->filename);
             return AP_FILTER_ERROR;
         }