Avoid preloading classes for boot image profiling

Since the clinits may execute methods, we should avoid preloading
classes to avoid executing methods that may not be required. These
samples could cause inaccuracy in the boot image profile.

Test: manual: adb logcat | grep preloadClasses
Bug: 139883463

Change-Id: I5b4568a477724606105196cba010109f80eecec1