[BUG] Raft import changed

[jnke2016]

Describe the bug
The new raft conda packages recently deployed are a breaking change for cuGraph as it substitutes raft with raft-dask and pylibraft. This breaks the way raft is currently imported as it can be observed from the error traceback below

>>> import raft
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'raft'

The new way of importing raft is described as below

>>> import raft_dask
>>> 

This change affect couple raft utils currently used by cugraph like the default_client, raftComms, get_raft_comm_state, and get_client