Fix type on py3
Fix type on py3

This shouldn't have any practical effect, since *any* False-y value for
chunk will give us the correct behavior, but let's be consistent in the
type used with that name.

Change-Id: I1928883792e7a9945f3731ddeea992d14882d679

tipabu/swift,tipabu/swift,openstack/swift,swiftstack/swift,openstack/swift,swiftstack/swift,tipabu/swift,openstack/swift,swiftstack/swift,tipabu/swift,openstack/swift