Don't try to remove Cargo.lock if it doesn't exist.

Change-Id: Ibfad6d97988edb6305d7a237d038412ec5a6100f

scripts/cargo2android.py

@@ -1370,6 +1370,7 @@ class Runner(object):
     os.environ['PATH'] = saved_path
     if not self.dry_run:
       if not had_cargo_lock:  # restore to no Cargo.lock state
+        if os.path.exists(cargo_lock):
           os.remove(cargo_lock)
       elif not self.args.use_cargo_lock:  # restore saved Cargo.lock
         os.rename(cargo_lock_saved, cargo_lock)