Fix inference regression, private model loading, and catch the timeout error when waiting for Vespa converge

[wanliAlex]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) Bug fix

• What is the current behavior? (You can also link to an open issue here)

  1. we call empty cash after each vectorise -> encode call
  2. There is a private model loading regression

• What is the new behavior (if this is a feature change)?

  1. We fix the latency speed regression
  2. We fix the private model loading regression
  3. Catch the timeout error when waiting for Vespa converge

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?) no

• Have unit tests been run against this PR? (Has there also been any additional testing?)

• Related Python client changes (link commit/PR here)

• Related documentation changes (link commit/PR here)

• Other information:

• Please check if the PR fulfills these requirements

• [ ] The commit message follows our guidelines

• [ ] Tests for the changes have been added (for bug fixes/features)

• [ ] Docs have been added / updated (for bug fixes / features)

[vicilliar]

We should probably add the 3rd change "Catch the timeout error when waiting for Vespa converge" to PR name and merge commit message for easier traceability.