Create a logger class to intercept tracebacks from sandesh

[Adam Wierzbicki]

There are cases when tests pass, but nonetheless some error tracebacks appear in sandesh logs. In order to avoid such situations we need a custom logger class which could intercept sandesh logger calls and make test cases to fail when errors appear.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/33539
Submitter: Adam Wierzbicki (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/33539
Committed: http://github.com/Juniper/contrail-controller/commit/d1d4817d95be5ac0b58eb4ad461186d9cbf955c7
Submitter: Zuul (<email address hidden>)
Branch: master

commit d1d4817d95be5ac0b58eb4ad461186d9cbf955c7
Author: Adam Wierzbicki <email address hidden>
Date: Tue Jul 11 17:48:51 2017 +0200

Automated monitoring logs for tracebacks

ErrorInterceptingSandeshLogger is a custom SandeshLogger class which
allows to intercept calls containing tracebacks. They are stored in
a class variable and can be used in a test to assert that no traceback
appeared during test execution. Base class for kube-manager tests was
modified to use this logger.

Related-Bug: #1703837
Change-Id: I78a970b1cdf18aa9b368b869207f3413018dc952