Scope of abort_on_config_error is too large

[Mostafa Mokhtar]

When deploying Impala on hosts without a co-located HDFS Data node Impala
won't start, unless abort_on_config_error=false is passed as a safety valve.

Concern is that abort_on_config_error checks more than just Short circuit
reads.

Does it make sense to move Short circuit read check out of
abort_on_config_error or put it in a separate flag?

fe/src/main/java/org/apache/impala/service/JniFrontend.java
  /**
   * Returns an error string describing all configuration issues. If no
config issues are
   * found, returns an empty string.
   */
  public String checkConfiguration() {
    StringBuilder output = new StringBuilder();
    output.append(checkLogFilePermission());
    output.append(checkFileSystem(CONF));
    output.append(checkShortCircuitRead(CONF));
    return output.toString();
  }

be/src/service/impala-server.cc
  Status status = exec_env_->frontend()->ValidateSettings();
  if (!status.ok()) {
    LOG(ERROR) << status.GetDetail();
    if (FLAGS_abort_on_config_error) {
      CLEAN_EXIT_WITH_ERROR(
          "Aborting Impala Server startup due to improper configuration");
    }
  }

  status = exec_env->tmp_file_mgr()->Init(exec_env->metrics());
  if (!status.ok()) {
    LOG(ERROR) << status.GetDetail();
    if (FLAGS_abort_on_config_error) {
      CLEAN_EXIT_WITH_ERROR("Aborting Impala Server startup due to
improperly "
           "configured scratch directories.");
    }