This is general clean up in prep for use with the stress test.
Changes:
1) Failed commands and failure to connect now raise exceptions.
Previously run_cmd() was not guaranteed to do anything at all in
remote mode.
2) Fix scope of 'hosts' which was at the class level but was modified
by instance level functions which makes no sense since different
instances could clash with each other.
3) Remove uses of opaque *args and **kwargs instead of named args. The
generic forms should be avoided since they impair readability.
4) Stop trying to get the cluster hosts from an environment variable
unconditionally upon construction.
5) Remove 'local' member variable, it's not needed and allowing 'local'
to be set to False when no 'hosts' are not set makes no sense.
6) Simplify and remove unneeded methods and arguments.
Change-Id: Id90bd3b640f2681bb7e82a5e6d5e49ed8c5a7b98
Reviewed-on: http://gerrit.cloudera.org:8080/514
Reviewed-by: Casey Ching <casey@cloudera.com>
Tested-by: Internal Jenkins
