Revert f8f72a17 ([erp5] don't use caucase generated certificate for now, 2019-03-12) since nothing prevents us drom using caucase certificate now.

Use managed resources to simplify existing tests and introduce tests for:

Access Log

• balancer partition should produce logs in apache "combined" log format with microsecond timing of requests.
• these logs should be rotated daily
• an apachedex report is ran on these logs daily.

Balancing

• requests are balanced to multiple backends using round-robin algorithm
• if backend is down it is excluded
• a "sticky cookie" is used so that clients are associated to the same backend
  • the cookie is set by balancer
  • when client comes with a cookie it "sticks" on the associated backend
  • if "sticked" backend is down, another backend will be used

Content-Encoding

• balancer encodes responses in gzip for some configured content types.

HTTP

• Server uses HTTP/1.1 or more and keep connection with clients

TLS (server certificate)

In this MR we also change apache to use a caucase managed certificate and add test coverage for:

• balancer listen on https with a certificate that can be verified using the CA from caucase.
• balancer uses the new certificate when its own certificate is renewed.

But we don't add support for:

• balancer can be instantiated with a certificate and key passed as SlapOS request parameters (code here) this use case is the job of caucase, so we no longer support this.

TLS (client certificate)

• balancer verifies frontend certificates from frontend caucases ( also tested in "Forwarded-For" section )
• if frontend provided a verified certificate, balancer set remote-user header
• balancer updates CRL from caucases ( caucase-updater-housekeeper )
• (NOT TESTED) balancer updates CA certificate from caucase ( caucase-updater-housekeeper ). Since this is would be complex to test and basic functionality of caucase-updater-housekeeper for frontend caucases is covered by CRL test, we don't test this for simplicity.

"Forwarded-For" header

This was also covered by existing tests:

• balancer set X-Forwarded-For header when frontend certificate can be verified
• balancer strips existing X-Forwarded-For

Integration with the rest of ERP5 software release

This was also covered by existing tests:

• The https URL of each Zope family is published and replies properly
• Some https URLs are generated for runUnitTest, so that test run with an https certificate. This is also covered by regular ERP5 functional tests.