RFR: 8227651: Tests fail with SSLProtocolException: Input record too big

[Daniel Jeliński]

Fix `SSLEngineService` test class to make sure it does not discard any network data between `handshaking` and `receive`.

With TLS1.3 the client starts sending application data immediately after sending the Finished message. The server may read some of that data in the `handshaking` method. This patch makes sure that any such data is delivered to the `receive` method for processing.

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Commit messages:
 - Preserve excess network data

Changes: https://git.openjdk.org/jdk/pull/9773/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9773&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8227651
  Stats: 51 lines in 8 files changed: 5 ins; 5 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/9773.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9773/head:pull/9773

PR: https://git.openjdk.org/jdk/pull/9773