don't add user site dir to sys.path

This is to avoid the following SELinux denial on F-20:

avc:  denied  { search } for  pid=18286 comm="osa-dispatcher"
name=".local" dev="dm-0" ino=262158
scontext=system_u:system_r:osa_dispatcher_t:s0
tcontext=system_u:object_r:gconf_home_t:s0 tclass=dir