Fix memory leak in WifiLegacyHal. am: 84310761ce

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

Change-Id: I6930efc7dfd370c58e9c4f9edda19e356cd51c96
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>