Fix libosv build with python 2

Commit c00e6e14bc0164b5bb38b723ac1499fa4b9028b9 attempted to fix libosv.py
to also support python 2, but it used a "__future__" import statement
which was not necessary, and doesn't work (Python 2.7.5 says it is misplaced
and aborts).

Removing this statement makes build work again on Fedora 20 with its
Python 2.7.5.

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
build.mk: move modules/tests/usr.manifest to build/

Move modules/tests/usr.manifest into build/$(mode)/
The modules/tests/usr.manifest file is generated during 'make image=tests' and appears
as untracked in 'git status'. Moving it inside build/ gets rid of the message.

Signed-off-by: Jaspal Singh Dhillon <jaspal.iiith@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
top.py: add tie-breaker sort criterion

Usually we have just a few threads with non-zero CPU usage, and the rest
are tied at 0%. Add a secondary sorting criterion, which is the total
CPU time. So now after all the threads using CPU now, we see the threads
that have been using a lot of CPU time in the past, instead of just a bunch
of random threads.

Reviewed-by: Tomasz Grabiec <tgrabiec@gmail.com>
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Merge branch 'master' of https://github.com/cloudius-systems/osv