Fix memory leak in WifiLegacyHal. am: 84310761ce am: aa1f8755c8

Original change: https://googleplex-android-review.googlesource.com/c/platform/hardware/interfaces/+/23772717

Change-Id: I0954dbcf561b6e16bb98ebb69fa5238031eea0f1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>