Fix failure in multi-chunk state sync for nicira plugin

Bug 1224719

This patch ensures the 'result_count' attribute from NVP API responses
is properly handled, and adds support for '_page_cursor' request query
parameter in the fake nvp api client in order to ensure issues like this
are captured by unit tests.

Change-Id: I1d6179bd58a14d19729fc882f004b6d1afccbe3d
Merge "Fix failure in multi-chunk state sync for nicira plugin"