nghttpx: Lesser usage of DIE

src/shrpx_http2_session.cc

@@ -602,7 +602,8 @@ int Http2Session::initiate_connection() {
   }
 
   // Unreachable
-  DIE();
+  assert(0);
+
   return 0;
 }
 

src/shrpx_http2_upstream.cc

@@ -1360,7 +1360,7 @@ int Http2Upstream::rst_stream(Downstream *downstream, uint32_t error_code) {
   if (rv < NGHTTP2_ERR_FATAL) {
     ULOG(FATAL, this) << "nghttp2_submit_rst_stream() failed: "
                       << nghttp2_strerror(rv);
-    DIE();
+    return -1;
   }
   return 0;
 }

src/shrpx_spdy_upstream.cc

@@ -854,7 +854,7 @@ int SpdyUpstream::rst_stream(Downstream *downstream, int status_code) {
   if (rv < SPDYLAY_ERR_FATAL) {
     ULOG(FATAL, this) << "spdylay_submit_rst_stream() failed: "
                       << spdylay_strerror(rv);
-    DIE();
+    return -1;
   }
   return 0;
 }