2751: Added code to recognize keep proxies in the keep_disks() response and set
using_proxy flag.  Added support for 'X-Keep-Desired-Replication' and
'X-Keep-Replicas-Stored' HTTP headers.  Added ARVADOS_KEEP_PROXY environment
variable.
2751: Added support for keep_services table, can still use keep_disks as a fallback.
2751: Added support for keep_services table, can still use keep_disks as a fallback.
2751: merge because git derp.
Merge branch 'master' into 2751-python-sdk-keep-proxy-support
Merge branch '2798-go-keep-client' into 1885-keep-proxy
1885: Stubbed out integration test for proxy
1885: Integration test of proxy work in progress.
Merge remote-tracking branch 'origin/master' into 1885-keep-proxy
1885: Full-stack integration test (api+keep+keepproxy+keepclient) works!
1885: GET and HEAD through the proxy work correctly now.  Added invalid API token test.
Merge branch 'master' into 1885-keep-proxy
1885: Made ServiceRoots atomically updatable, so that KeepProxy can poll for
changes in the services list without disrupting any active flows.
1885: Fix bug in not returning from the handler on failed authorization.
Improved logging (which uncovered the previous bug.)  Tweaked go.sh and tests.
Merge branch 'master' into 1885-keep-proxy
1885: Added logging of invalid requests.  Added logging when the server list is
update.  Improved KeepClient error reporting.
Merge branch '1885-keep-proxy' into 2751-python-sdk-keep-proxy-support
2751: Teaching run_test_server how to run the proxy server for testing.  Added -pid option to keep server.
Merge branch 'master' into 2751-python-sdk-keep-proxy-support refs #2751
2751: Changed to "except:" to "except Exception:".  Refactored environment setup in keep_client_Test to be a bit more robust.