[BUG][Weighted Shard Routing] Fail open count is not updated for only healthy copy in weighed away az

[anshu1106]

Describe the bug
Fail Open stats added as part of PR does not update fail open count if there is a fail open executed due to single healthy shard copy and that copy resides in weighed away az data node.

To Reproduce
Steps to reproduce the behavior:

1. Create a domain with 3 azs (3 shard copies) and set shard routing weight to 0 for one of the azs.
2. Inject faults(fail all copies of a shard except the one in weighed away az) so that fail open is executed for shard search request.
3. Make node stats api call GET /_nodes/<node_id>/stats/weighted-routing
4. Fail open count is not updated

Expected behavior
Fail open count should increase on fail open execution.

Plugins
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Screenshots
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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Version [e.g. 22]

Additional context
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