RebootEscrow HAL: testing with secure implementations

To test implementations that use TEE keymaster with EARLY_BOOT_ONLY
keys, it is required that the "earlyBootEnded" call in vold should be
removed before they will pass. Mark those tests as DISABLED_... and
include a comment and README indicating what needs to be done.

Bug: 159513354
Bug: 158964050
Test: atest VtsHalRebootEscrowTargetTest
Change-Id: Ie12969c0353ff42202b3dfcfa0be87ba3442e5d3