readAndValidateLockNVIndexPublic needs to attempt a TPM2_NV_Read command

[chrisccoulson]

readAndValidateLockNVIndexPublic is used to ensure that the supplied NV index is safe to use in an authorization policy during key sealing, but it isn't safe if the index has a non-empty authorization value even if the public area appears to be ok, as a non-empty authorization value will cause TPM2_NV_ReadLock to fail.