Fix TS-1707: Calculate blocks correctly on FreeBSD
Fix TS-1707: Calculate blocks correctly on FreeBSD

FreeBSD calculation of

    blocks = size / hw_block_size;

is wrong, because *our* *store* block size defaults to 8k.

I'm further adding comments for future reference in other code paths.

TS-1707 further reminds us that these triple (or more) code paths
are confusing at best, and should be unified.

taoyunxing/trafficserver,PSUdaemon/trafficserver,duke8253/trafficserver,davidbz/trafficserver,reveller/trafficserver,bryancall/trafficserver,vmamidi/trafficserver,rahmalik/trafficserver,vmamidi/trafficserver,clearswift/trafficserver,dyrock/trafficserver,davidbz/trafficserver,reveller/trafficserver,bryancall/trafficserver,chenglongwei/trafficserver,PSUdaemon/trafficserver,dyrock/trafficserver,chitianhao/trafficserver,davidbz/trafficserver,davidbz/trafficserver,chenglongwei/trafficserver,chitianhao/trafficserver,rahmalik/trafficserver,PSUdaemon/trafficserver,bryancall/trafficserver,taoyunxing/trafficserver,chitianhao/trafficserver,rahmalik/trafficserver,clearswift/trafficserver,SolidWallOfCode/trafficserver,rahmalik/trafficserver,taoyunxing/trafficserver,persiaAziz/trafficserver,chenglongwei/trafficserver,duke8253/trafficserver,rpufky/trafficserver,persiaAziz/trafficserver,SolidWallOfCode/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,taoyunxing/trafficserver,taoyunxing/trafficserver,chitianhao/trafficserver,rpufky/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,bryancall/trafficserver,bryancall/trafficserver,vmamidi/trafficserver,duke8253/trafficserver,SolidWallOfCode/trafficserver,reveller/trafficserver,rpufky/trafficserver,SolidWallOfCode/trafficserver,SolidWallOfCode/trafficserver,persiaAziz/trafficserver,reveller/trafficserver,persiaAziz/trafficserver,rpufky/trafficserver,PSUdaemon/trafficserver,duke8253/trafficserver,rpufky/trafficserver,chenglongwei/trafficserver,taoyunxing/trafficserver,dyrock/trafficserver,PSUdaemon/trafficserver,pbchou/trafficserver,duke8253/trafficserver,reveller/trafficserver,clearswift/trafficserver,reveller/trafficserver,reveller/trafficserver,rahmalik/trafficserver,rahmalik/trafficserver,vmamidi/trafficserver,dyrock/trafficserver,pbchou/trafficserver,vmamidi/trafficserver,rpufky/trafficserver,persiaAziz/trafficserver,clearswift/trafficserver,rahmalik/trafficserver,chitianhao/trafficserver,taoyunxing/trafficserver,rpufky/trafficserver,davidbz/trafficserver,davidbz/trafficserver,taoyunxing/trafficserver,rpufky/trafficserver,pbchou/trafficserver,duke8253/trafficserver,clearswift/trafficserver,bryancall/trafficserver,pbchou/trafficserver,persiaAziz/trafficserver,pbchou/trafficserver,chenglongwei/trafficserver,persiaAziz/trafficserver,chenglongwei/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,rahmalik/trafficserver,clearswift/trafficserver,clearswift/trafficserver,chenglongwei/trafficserver,persiaAziz/trafficserver,chitianhao/trafficserver,PSUdaemon/trafficserver,PSUdaemon/trafficserver,rahmalik/trafficserver,reveller/trafficserver,rpufky/trafficserver,duke8253/trafficserver,pbchou/trafficserver,SolidWallOfCode/trafficserver,dyrock/trafficserver,vmamidi/trafficserver,dyrock/trafficserver,taoyunxing/trafficserver,chitianhao/trafficserver,chenglongwei/trafficserver,reveller/trafficserver