http: adjust test threshold for larger suse buffers
http: adjust test threshold for larger suse buffers

My theory is that suse has larger TCP buffer sizes
by default.  I now check over 100MB, rather than over 2MB.
100MB is ~halfway between the 1MB limit and the 200MB
request that's attempted.

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/4926048

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang