gRPC: fixed missing state save in frame header parsing.

Previously, frame state wasn't saved if HEADERS frame payload
that begins with header fragment was not received at once.

src/http/modules/ngx_http_grpc_module.c

diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
index 5ec45e2..b6be9b8 100644
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -2410,6 +2410,7 @@
         }
 
         ctx->padding = 0;
+        ctx->frame_state = state;
     }
 
     if (state < sw_fragment) {