Simplify AudioRecord::restoreTrack_l()

Finish removing CBLK_RESTORING and CBLK_RESTORED from control block flags,
and remove constant RESTORE_TIMEOUT_MS.

Also minor cleanup:
 - Cache mCblk in local variable cblk and make cblk allocatable in a register.
 - Use "iMem" for sp<IMemory>.
 - Add missing error log to AudioRecord; it was already in AudioTrack.

This is part of a series to clean up the control block.

Change-Id: Ia5f5ab4763c392bc06a45851b167ddaee29e3455