Wrap the import of psutil in a try/catch to unbreak the full CDH build.
Wrap the import of psutil in a try/catch to unbreak the full CDH build.

buildall invokes start-impala-cluster.py --kill --force in order to ensure that there are
no Impala daemons running on the system. The recent introduction of psutil in the start
script breaks the full CDH build as it's not a standard python module.

This patch only imports psutil inside the method its used and disables its usage with a
warning in the case that it's not found.

Change-Id: Ic2fce81b6d7af2722e0e23c2a580c30b86144aa1
Reviewed-on: http://gerrit.cloudera.org:8080/540
Reviewed-by: Ishaan Joshi <d1d1e60202ec9f2503deb1b724986485a125d802@cloudera.com>
Tested-by: Internal Jenkins

cloudera/recordservice,cloudera/recordservice,cloudera/recordservice,cloudera/recordservice,cloudera/recordservice,cloudera/recordservice,cloudera/recordservice