Handle cases where environment variables are not defined in impala-config.sh
Handle cases where environment variables are not defined in impala-config.sh

Change-Id: Iee2800cb02299a9ed26da6fd079e3a72fe2a2482
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2537
Reviewed-by: Lenni Kuff <724b7df200764f5dc1b723c05ee6c6adabd11bb1@cloudera.com>
Tested-by: Lenni Kuff <724b7df200764f5dc1b723c05ee6c6adabd11bb1@cloudera.com>
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2539

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