Similar to commit 31ab78ae

Fixes deadlock because FileInputStream::Read() unlocks the mutex
(which was not locked) and then locks it, keeping it locked.  This can
result in a deadlock.  This happens because the archive and the file
mutex are different.

Fixes thread sanitizer warnings.

Fixes thread sanitizer warnings.

Use the "==" operator instead of pthread_equal().

This allows us to eliminate two boolean flags which are there to avoid
race conditions, and made the thing so fragile that I got tons of
(correct) thread sanitizer warnings.

Use one single std::lock_guard in Run(), and replace the manual
Lock()/Unlock() calls.

Eliminate more unlock/lock transitions, making the code more robust.

Regression from commit 0772e571

Reduces main thread contention.  Avoids blocking the main thread in
"status" commands.