Increase the memory disk size in the following testcases to avoid mount
failures, which would cause cascade failures in the rest of the test
run:

link/15.t, open/19.t, mkdir/11.t, mkfifo/11.t, symlink/11.t

Fail quickly in all of the testcases if mdconfig, mount, umount, etc
fails to avoid issues similar to this in the future

Submitted by: Casey Peel <cpeel@isilon.com>
MFC after: 2 weeks
X-MFC with: r272057
Sponsored by: EMC / Isilon Storage Division