fix hang in `./openbazaar stop`

Sometimes `./openbazaar stop` fails to stop the server and ends up hanging itself too.

Recently it seems we have picked up a crash that once again requires sigkill. I think sigkill never did work with the new stop function maybe.

Currently, if sigterm doesn't work and `psutil.wait_procs()` is called, it never returns. We don't need to call that anyway.

Further testing is warranted. I'm posting this now because I don't want to lose track of it while I'm working on other things.
I recommend using the old-style `print` for now; I will port the code in a consistent manner in the future. The parentheses aren't benign (and that's why I have pylint flag the code):
```
renelvon @ merchant ~ % python2
Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print "a", "b"
a b
>>> print("a", "b")
('a', 'b')
>>> from __future__ import print_function
>>> print("a", "b")
a b
>>> 
```