Enable Clippy and fix warnings am: 2b13024f5f

Original change: https://android-review.googlesource.com/c/trusty/app/keymint/+/3105940

Change-Id: I25fda0537b0434d2c5def9106598e5dc38a5ba9b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>