BpfMap: enforce BPF_F_RDWR_EXCLUSIVE doesn't use cached fd. am: 2f50623b0e

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3134195

Change-Id: Ia0c699bc687c12589e42feb40f62391dcbce1a01
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>