Remove obsolete tempest-lib
Remove obsolete tempest-lib

tempest-lib has been reintegrated into tempest and this repository
already uses tempest instead of tempest-lib. Replace requirements for
tempest-lib with requirements for tempest.

See also
https://specs.openstack.org/openstack/qa-specs/specs/tempest/implemented/reintegrate-tempest-lib.html

Change-Id: I74350fbd81ccfafa9080a437cfa5d95a7a561159

stackforge/networking-bigswitch,wolverineav/networking-bigswitch,stackforge/networking-bigswitch,wolverineav/networking-bigswitch,openstack/networking-bigswitch,openstack/networking-bigswitch