Migrate cli test framework to tempest-lib

This commit switches the cli tests to use tempest-lib. The code which
was migrated to tempest-lib is removed and all the existing test cases
are converted to use the framework provided by the library. Future
improvements to the cli testing framework should be made in
tempest-lib after this commit.

Partially implements bp tempest-library
Change-Id: If2c9b3895a30905bc3d62b8daef783878d78399a
Switch to using subunit-trace from tempest-lib

This commit removes the tempest copy of subunit-trace and uses the
entry-point from tempest-lib instead.

Partially implements bp tempest-library

Change-Id: Ic1aeddc2d0b217c41b6b9914ac3f269b80c4ec8e
Merge "Migrate cli test framework to tempest-lib"
Merge "Switch to using subunit-trace from tempest-lib"
Merge branch 'master' of https://github.com/openstack/tempest