Revert use of netapp_lib from NetApp Drivers

Revert use of netapp_lib from NetApp Drivers

This patch cleanly reverts the changes made via the
commit: e681ba2a99995dcd999e6539bb1222f8a1ac8adc
cleanly and mitigates the conflicts that would
occur with git-revert on the said commit.

The revert is solely for changes pertaining to the use
of the external library, netapp_lib. Minor code refactors
from the prior change are retained.

Unit test coverage has been increased for ZAPI and REST
interface code in netapp/dataontap/client/api.py and
netapp/eseries/client.py.

Closes-Bug: #1499334
Change-Id: Icead7e168e1c7187840de87c69365d26aedd5924
(cherry picked from commit ff81307ca4c796a66f4bd584b4633db07dcf2a16)