[lio-py]: Add lio_err() usage w/ sys.exit(1) for errors
[lio-py]: Add lio_err() usage w/ sys.exit(1) for errors

This patch updates lio_node.py to use lio_err() when handling error conditions
that return a non-zero condition to the caller.  Previously most locations
in lio_node.py had been using 'return -1' for exceptions which does NOT translate
to a non-zero sys.exit() call.

This patch updates all these cases to use lio_err() as well as adds a few additional
exception cases in lio_target_del_iqn(), lio_target_del_tpg(), lio_target_add_np(),
and lio_target_del_np()

Signed-off-by: Nicholas A. Bellinger <978acd1567d5598152161fdf8bf3ca568f950c9b@linux-iscsi.org>

Datera/lio-utils,Datera/lio-utils,Datera/lio-utils,Datera/lio-utils