Guard against os-log-merger failure
Guard against os-log-merger failure

At the moment, the tool may crash parsing some files, which renders the
whole run failed. Until we fix that in the next os-log-merger, just
ignore failures and proceed. Of course, that will mean no -index.txt
file generated, or with incomplete data. Still better than just
invalidating the test run.

Change-Id: I28300de31ed49b1a21e4c1ed1f7d10f90943878b

openstack/neutron,eayunstack/neutron,mahak/neutron,huntxu/neutron,openstack/neutron,noironetworks/neutron,eayunstack/neutron,noironetworks/neutron,huntxu/neutron,openstack/neutron,mahak/neutron,mahak/neutron