rteval: Fix sysreport traceback when utility sos not found

When rteval is run with
-s, --sysreport       run sysreport to collect system data (default: False)

and sos, sosreport or sysreport cannot be found then rteval exits with
an error.

Fix this by adding /usr/bin to the places to search for this program.

Signed-off-by: John Kacur <jkacur@redhat.com>