Add testcase to verify if service user exists with admin role.
Add testcase to verify if service user exists with admin role.

     - Verify service user availability

Change-Id: I9ba386fecb6a80d3011260f39752f9d7d8f26567
Signed-off-by: manashsarma <bc095463df3ac81e71d6b05cdcfc30e87ec3c38e@in.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation