RFR: 8259223: Simplify boolean expression in the SunJSSE provider

[Xue-Lei Andrew Fan]

There are some boolean expressions that could be improved for better readability in the SunJSSE provider implementation. For example: 

- if (cert instanceof X509Certificate == false) { 
+ if (!(cert instanceof X509Certificate)) { 

- return isDTLS ? true : (id >= TLS10.id);
+ return isDTLS || (id >= TLS10.id);


Code cleanup, no new regression test.

Bug: https://bugs.openjdk.java.net/browse/JDK-8259223

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Commit messages:
 - 8259223: Simplify boolean expression in the SunJSSE provider

Changes: https://git.openjdk.java.net/jdk/pull/1942/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1942&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259223
  Stats: 35 lines in 11 files changed: 0 ins; 0 del; 35 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1942.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1942/head:pull/1942

PR: https://git.openjdk.java.net/jdk/pull/1942