incompatibility with a python client

2.6.6 stores a String value with flag=32 even with setPrimitiveAsString(true).
a python client (installed with pip install python-memcached) can not get the value.

MemCached: unknown flags on get: 20
 13: handler exception: local variable 'val' referenced before assignment

i guess it's better to use flag=0 for setPrimitiveAsString(true) clients as it seems that
older versions used to do.
