Fixed: workload_runner fails when there is an underscore in workload name

Change-Id: Ic18c5409f87c14b4b3f80baef1302a1d9cff3bc9
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3745
Reviewed-by: Taras Bobrovytsky <tbobrovytsky@cloudera.com>
Tested-by: jenkins
(cherry picked from commit 2d82416a0b1883b80e1295a2ab72d992ca3cf519)
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4048