IMPALA-2001: Check for running processes during startup and killing.
IMPALA-2001: Check for running processes during startup and killing.

This patch checks that the processes launched by start-impala-cluster.py
are actually started or killed. During startup, it checks if the
appropriate processes are really killed. This is useful in cases where a
similar process was started by another user and thus preventing starting
this mini cluster. For the statestore and the catalog this patch adds an
additional check after the processes were launched to verify their
existence.

Change-Id: Idfd6a11fd72278ddf180dc537459582b4392a109
Reviewed-on: http://gerrit.cloudera.org:8080/521
Tested-by: Internal Jenkins
Reviewed-by: Ishaan Joshi <d1d1e60202ec9f2503deb1b724986485a125d802@cloudera.com>

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