BUG/MINOR: mux-fcgi: Set conn state to RECORD_P when skipping the record padding

When the padding of a "stream" record (STDOUT or STDERR) is skipped, we must set
the connection state to RECORD_P. It is especially important if the padding is
not fully received.

This patch must be backported as far as 2.1.
diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index d1094d9..efe5d54 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -2295,6 +2295,7 @@
 		goto fail;
 
   end_transfer:
+	fconn->state = FCGI_CS_RECORD_P;
 	fconn->drl += fconn->drp;
 	fconn->drp = 0;
 	ret = MIN(b_data(&fconn->dbuf), fconn->drl);
@@ -2379,6 +2380,7 @@
 		goto fail;
 
   end_transfer:
+	fconn->state = FCGI_CS_RECORD_P;
 	fconn->drl += fconn->drp;
 	fconn->drp = 0;
 	ret = MIN(b_data(&fconn->dbuf), fconn->drl);