Up some delays and timeouts in the test

This doesn't affect what the test is testing, but makes it more likely
for the test to succeed on OSs that timeout on writes differently than
in a unix like system which uses epoll.

Specifically, Akaros times out each write using an alarm to trigger an
abort_syscall() system call.  This method causes problems for the test,
however, because system calls can only be aborted at specific
synchronization points, not while in the middle of an operation (i.e.
they can only be aborted when sitting inside a rendvous sleep).  If the
abortion fails, we reset the alarm with a certain delay (currently 1
second) and retry the abort later.

Because of the periodic nature of the abort retries and the fact that
the read and the write are mostly running in lock-step, its hard to
actually hit the case where we end up aborting the write.
Adding these new delays and the new timeout value compensate for this
and make the test more reliable on Akaros without affecting other
systems.
Partially revert b0a0eb0abdc48c0a0640d7b11fc1f923acd45fac

Not building for akaors breaks some of the test infrastructure when
building.  We just conditionally don't run the test for akaros inside
the tests themselves (just like is being doen for plan9 as well).
Add longer timeout for akaros

We need longer than a 2 minute timeout for some of the akaros tests.
This is likely due to the fact that we run the tests in quemu, but
that's the way we are doing things for now, so we need this extra slack.
Update to README

Busybox instructions were slightly incorrect
Allow ifconfig and root scripts to take params

This requires a cahnge to the default root script in akaros.  That's
fine though.  It's more consistent the new way anyway, and I was the
only one really using it the old way.