(core) freshen tests for python3

Summary:
Recent python3 changes perturbed timing again, and a few more tests started failing.

Contains an unrelated correction for gvisor running under docker (a useful configuration on macs for debugging gvisor problems, but not supported by throttling code).

Test Plan: updated tests

Reviewers: dsagal, alexmojaki

Reviewed By: dsagal, alexmojaki

Differential Revision: https://phab.getgrist.com/D3129

app/server/lib/SandboxControl.ts

@@ -104,6 +104,7 @@ export class SubprocessControl implements ISandboxControl {
   private _throttle?: Throttle;
   private _monitoredProcess: Promise<ProcessInfo|null>;
   private _active: boolean;
+  private _foundDocker: boolean = false;
 
   constructor(private _options: {
     pid: number,   // pid of process opened by Grist
@@ -134,6 +135,10 @@ export class SubprocessControl implements ISandboxControl {
   }
 
   public async kill() {
+    if (this._foundDocker) {
+      process.kill(this._options.pid, 'SIGKILL');
+      return;
+    }
     for (const proc of await this._getAllProcesses()) {
       try {
         process.kill(proc.pid, 'SIGKILL');
@@ -179,7 +184,10 @@ export class SubprocessControl implements ISandboxControl {
         const recognizer = this._options.recognizers[key];
         if (!recognizer) { continue; }
         for (const proc of processes) {
-          if (proc.label.includes('docker')) { throw new Error('docker barrier found'); }
+          if (proc.label.includes('docker')) {
+            this._foundDocker = true;
+            throw new Error('docker barrier found');
+          }
           if (recognizer(proc)) {
             recognizedProcesses[key] = proc;
             continue;