make taskFailed non-fatal

turns out we can end up here when an http client unexpectedly
drops the connection, so it must not cause an exit()

src/server.cpp

@@ -157,7 +157,5 @@ kj::Promise<void> Server::handleFdRead(kj::AsyncInputStream* stream, char* buffe
 
 void Server::taskFailed(kj::Exception &&exception) {
     //kj::throwFatalException(kj::mv(exception));
-    // prettier
-    fprintf(stderr, "fatal: %s\n", exception.getDescription().cStr());
-    exit(EXIT_FAILURE);
+    fprintf(stderr, "taskFailed: %s\n", exception.getDescription().cStr());
 }