Clarify confusions between atomic_t and bitmap.  Fix bitmap operations
accordingly.
Fix the incomplete conversion from atomic_t to long for test_bit().
Bump up the default timeouts for move commands in the ch(4) driver
to 15 minutes, and 5 minutes for things like READ ELEMENT STATUS.

This is needed to account for the worst case scenarios on at least
some Spectra Logic tape libraries.

Sponsored by:	Spectra Logic
MFC after:	3 days