Stop isReady method always returning true

The OvsdbClientImpl.isReady() method will always return true as the
schema variable is initialized when the class is created and an
instance of a list can never be null.

This commit implements the timeout in the ToDo and changes the logic
to check if the schema.isEmpty

Change-Id: I1d48fa56f5a93e227fc3b623d3405d07a1751972
Signed-off-by: Dave Tucker <djt@redhat.com>
Merge "Stop isReady method always returning true" into topic/schema