FetchAction: Fix FloggerFormatString pattern flagged by error prone

Build is failing with recent Error Prone version:

  FetchAction.java:135: error: [FloggerFormatString]
  extra format arguments: used 0, provided 3
        log.atSevere().withCause(e).log(
                                       ^
    (see https://errorprone.info/bugpattern/FloggerFormatString)

Change-Id: Ice44e15d86f7c07d79a996fca18677efc44400a0