The reservationId is an internal field used for RESERVATION requests and
acts much like an internal, unique NetworkSpecifier value. A
NetworkRequest with a reservationId set can be satisfied by a Network /
Offer with the same reservationId or an Offer with the wildcard {@code
RES_ID_MATCH_ALL_RESERVATIONS}.
Regular requests do not set the reservationId and match any Network /
Offer (except the blanket offer) independent of their reservationId.
Test: NetworkCapabilitiesTest
Change-Id: Id06116adf776dbf09cb9f8ccb7f25ff51734e02e
cb91a25bb7