Enabled TestSetWatchlocation.py on Linux.

This worked 25 out of 25 times for me on Ubuntu 12.04 LTS x86_64 built
with gcc 4.8.2 and the July 2013 libedit.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@202516 91177308-0d34-0410-b5e6-96231b3b80d8