Revision 665233

Thrift: Python libraries install into /usr, not /usr/local

Summary:
It seems like the Python convention is that random janky libraries
are installed in /usr/lib/pythonX.Y/site-packages.  This patch follows
that convention, even though it is pretty gross to ignore --prefix.

Reviewed By: mcslee

Test Plan: make install thrift python libs on my box.

Revert Plan: ok