Merge "First-stage mount: avoid triggering a FATAL error"

FirstStageMount::FirstStageMount()

    : need_dm_verity_(false), device_tree_fstab_(fs_mgr_read_fstab_dt(), fs_mgr_free_fstab) {

    if (!device_tree_fstab_) {

        // The client of FirstStageMount should check the existence of fstab in device-tree

        // in advance, without parsing it. Reaching here means there is a FATAL error when

        // parsing the fstab. So stop here to expose the failure.

        LOG(FATAL) << "Failed to read fstab from device tree";

        LOG(INFO) << "Failed to read fstab from device tree";

        return;

    }

    // Stores device_tree_fstab_->recs[] into mount_fstab_recs_ (vector<fstab_rec*>)