Update exec script to synchronize on only running one at a time

Also move the mount point on the server to sit underneath
$GOROOT/misc/akaros/mnt
Remove the lock synchronization on the exec file

It really shouldn't be necessary.  Probably a bug in akaros for not
being able to run these tests in parallel.
Remove dependence on cpio.

All I care about is the binary anyway, so why bother archiving the whole
build directory on the server and unarchiving it on akaros. Just copy
over the binary itself.

I still put the binary into the same location it exists on the server
though, so we will ultimately be able to support running multiple
executables in parallel. (Though this doesn't seem to work for now --
probably an akaros bug).
Added a bunch of support scripts for akaros

These scripts simplify the task of setting up and running a 9p server
for akaros, as well as running a qemu instance of akaros that is capable of
running simple rpc calls.  The rest of the go scripts take advantage of
this rpc capability to run go executables remotely, but report the
results locally.