LibCore+RequestServer: Ignore callbacks for cancelled network jobs

Also cancel the jobs when they're destroyed.
This makes sure that jobs whose owners have discarded don't end up
crashing because of a did_fail().

Userland/Libraries/LibCore/NetworkJob.cpp

@@ -29,6 +29,9 @@ void NetworkJob::shutdown()
 
 void NetworkJob::did_finish(NonnullRefPtr<NetworkResponse>&& response)
 {
+    if (is_cancelled())
+        return;
+
     // NOTE: We protect ourselves here, since the on_finish callback may otherwise
     //       trigger destruction of this job somehow.
     NonnullRefPtr<NetworkJob> protector(*this);
@@ -42,6 +45,9 @@ void NetworkJob::did_finish(NonnullRefPtr<NetworkResponse>&& response)
 
 void NetworkJob::did_fail(Error error)
 {
+    if (is_cancelled())
+        return;
+
     // NOTE: We protect ourselves here, since the on_finish callback may otherwise
     //       trigger destruction of this job somehow.
     NonnullRefPtr<NetworkJob> protector(*this);
@@ -55,6 +61,9 @@ void NetworkJob::did_fail(Error error)
 
 void NetworkJob::did_progress(Optional<u32> total_size, u32 downloaded)
 {
+    if (is_cancelled())
+        return;
+
     // NOTE: We protect ourselves here, since the callback may otherwise
     //       trigger destruction of this job somehow.
     NonnullRefPtr<NetworkJob> protector(*this);

Userland/Services/RequestServer/GeminiRequest.cpp

@@ -58,7 +58,7 @@ GeminiRequest::~GeminiRequest()
 {
     m_job->on_finish = nullptr;
     m_job->on_progress = nullptr;
-    m_job->shutdown();
+    m_job->cancel();
 }
 
 NonnullOwnPtr<GeminiRequest> GeminiRequest::create_with_job(Badge<GeminiProtocol>, ClientConnection& client, NonnullRefPtr<Gemini::GeminiJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)

Userland/Services/RequestServer/HttpRequest.cpp

@@ -22,7 +22,7 @@ HttpRequest::~HttpRequest()
 {
     m_job->on_finish = nullptr;
     m_job->on_progress = nullptr;
-    m_job->shutdown();
+    m_job->cancel();
 }
 
 NonnullOwnPtr<HttpRequest> HttpRequest::create_with_job(Badge<HttpProtocol>&&, ClientConnection& client, NonnullRefPtr<HTTP::HttpJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)

Userland/Services/RequestServer/HttpsRequest.cpp

@@ -27,7 +27,7 @@ HttpsRequest::~HttpsRequest()
 {
     m_job->on_finish = nullptr;
     m_job->on_progress = nullptr;
-    m_job->shutdown();
+    m_job->cancel();
 }
 
 NonnullOwnPtr<HttpsRequest> HttpsRequest::create_with_job(Badge<HttpsProtocol>&&, ClientConnection& client, NonnullRefPtr<HTTP::HttpsJob> job, NonnullOwnPtr<OutputFileStream>&& output_stream)