RFR: 8275811 Incorrect instance to dispose

[Daniel Jeliński]

The current code that changes cipher suites disposes the new suite instead of the old one, which usually silently fails. This patch fixes the code to dispose the old instance instead.

DTLS appears to be unaffected: DTLSOutputRecord keeps 2 ciphers and correctly [disposes the old one](https://github.com/openjdk/jdk/blob/739769c8fc4b496f08a92225a12d07414537b6c0/src/java.base/share/classes/sun/security/ssl/DTLSOutputRecord.java#L106), and DTLSInputRecord [doesn't dispose anything](https://github.com/openjdk/jdk/blob/4b9303b77b43d890ebacbec38b4ac5db7e171886/src/java.base/share/classes/sun/security/ssl/DTLSInputRecord.java#L57)

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Commit messages:
 - Dispose correct cipher

Changes: https://git.openjdk.java.net/jdk/pull/6084/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6084&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275811
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6084.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6084/head:pull/6084

PR: https://git.openjdk.java.net/jdk/pull/6084