Use tempest.lib's base module for network clients

There is the same base modules on both tempest.lib and tempest.services.
tempest.lib is stable module now, and we can switch to use the module
for the code cleanup.

Partially implements blueprint migrate-service-clients-to-tempest-lib

Change-Id: I8d2b8e963b0dca9f3a3f70120c7c6d95313d022d
4 files changed