CLEANUP: http: rename http_process_request_body()

This function does not process anything, it just waits for the beginning
of the request body. Let's rename it http_wait_for_request_body().
diff --git a/src/session.c b/src/session.c
index b85f554..753d6cc 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1897,7 +1897,7 @@
 				}
 
 				if (ana_list & AN_REQ_HTTP_BODY) {
-					if (!http_process_request_body(s, s->req, AN_REQ_HTTP_BODY))
+					if (!http_wait_for_request_body(s, s->req, AN_REQ_HTTP_BODY))
 						break;
 					UPDATE_ANALYSERS(s->req->analysers, ana_list, ana_back, AN_REQ_HTTP_BODY);
 				}