Enable running in docker / k8s

When trying to run Brozzler in docker, we get the following error:
```
Failed to move to new namespace: PID namespaces supported, Network
namespace supported, but failed: errno = Operation not permitted
Trace/breakpoint trap
```
This happens because chromium uses sandboxing for increased security by
default and its not supported when running in a container.
Adding chromium option `--no-sandbox` fixes the problem.

This issue is common, I found various reports about it like this:
https://github.com/Zenika/alpine-chrome/issues/33

brozzler/chrome.py

@@ -170,7 +170,7 @@ class Chrome:
                 '--disable-background-networking',
                 '--disable-renderer-backgrounding', '--disable-hang-monitor',
                 '--disable-background-timer-throttling', '--mute-audio',
-                '--disable-web-sockets',
+                '--disable-web-sockets', '--no-sandbox',
                 '--window-size=1100,900', '--no-default-browser-check',
                 '--disable-first-run-ui', '--no-first-run',
                 '--homepage=about:blank', '--disable-direct-npapi-requests',