xfs/016: calculate minimum log size and end locations

xfs/016: calculate minimum log size and end locations

xfs/016 looks for corruption in the log when the log wraps.  However,
it hardcodes the minimum log size and the "95%" point where it wants to
start the "nudge and check for corruption" part of the test.  New
features require larger logs, which causes the test to fail when it
can't mkfs with the smaller log size and when that 95% point doesn't put
us within 20x "_log_traffic 2"s of the end of the log.

Fix the first problem by using the new min log size helper and replace
the 95% figure with an estimate of where we need to be to guarantee that
the 20x loop wraps the log.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>