Remove log spam.

When dumping, the code checks if a thread is running as a guest.
If it's not, the code always logs an error message if the header
data structure cannot be read. Don't print an error message in
this case.

Test: Crash and no longer see "failed to get the guest state header"
Test: message.
Change-Id: I6971b57b218a4f653682cfdc82118dc576d9e331