IMPALA-2819: kill cluster processes from Python
IMPALA-2819: kill cluster processes from Python

To avoid problems with the killall utility, use Python's psutil module.
This allows us to ignore "uid not found" error messages that can occur
when iterating over processes and trying to get the user ids.

As a bonus, this is slightly faster than the previous solution.

Change-Id: I486147e9b8054ee6bcfde50f5131d06ef721c5d9
Reviewed-on: http://gerrit.cloudera.org:8080/1852
Reviewed-by: Tim Armstrong <2f8e34250f03a653da3dc27f7ec203eafdde80fc@cloudera.com>
Tested-by: Internal Jenkins

ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC