Fix a log.F to log.Err
Fix a log.F to log.Err

There was a log.F in the trace client that would kill all of robot if
the trace ever failed. Changed it to an err instead.

ek9852/gapid,baldwinn860/gapid,Qining/gapid,google/agi,Qining/gapid,dsrbecky/gapid,dsrbecky/gapid,Qining/gapid,google/gapid,Qining/gapid,Qining/gapid,dsrbecky/gapid,dsrbecky/gapid,baldwinn860/gapid,ek9852/gapid,pmuetschard/gapid,baldwinn860/gapid,google/agi,google/agi,pmuetschard/gapid,pmuetschard/gapid,ek9852/gapid,ek9852/gapid,dsrbecky/gapid,baldwinn860/gapid,pmuetschard/gapid,google/agi,dsrbecky/gapid,dsrbecky/gapid,dsrbecky/gapid,baldwinn860/gapid,google/gapid,google/agi,google/gapid,ek9852/gapid,google/gapid,google/gapid,baldwinn860/gapid,google/gapid,Qining/gapid,google/agi,google/gapid,baldwinn860/gapid,ek9852/gapid,baldwinn860/gapid,google/agi,pmuetschard/gapid,pmuetschard/gapid,pmuetschard/gapid,google/gapid,Qining/gapid,google/agi,pmuetschard/gapid,Qining/gapid,ek9852/gapid,ek9852/gapid