Dispatcher has DISPATCH_WAIT_TIMEOUT_MSEC (current value is 2000) as poll
timeout. It waited for 30 iterations of poll to timeout before checking the
segment status. And then initiated fts probe before checking the segment
status. As a result it took ~minute for query to fail in case of segment
failures.

This commit updates to check segment status on every poll timeout. It also
leverages fts version to optimize whether to check segments. It avoids
performing fts probe, instead it relies on fts to be called on regular
intervals and provide cached results.

With this change test time for twophase_tolerance_with_mirror_promotion was cut
down by ~2 minutes.
Co-authored-by: NAshwin Agrawal <aagrawal@pivotal.io>