RFR: JDK-8257448: Clean duplicated non-null check in the SunJSSE provider implementation

[Xue-Lei Andrew Fan]

In the SunJSSE provider implementation, there are a few non-null check, used together with "instanceof" check.  For such cases, the non-null check is redundant as it could be covered by the "instanceof" check.  This update will remove the non-null check, like:
-   if ((cause != null) && (cause instanceof IOException)) { 
+  if (cause instanceof IOException) {

Code cleanup, no new regression text.

Bug: https://bugs.openjdk.java.net/browse/JDK-8257448

-------------

Commit messages:
 - 8257448: Clean duplicated non-null check

Changes: https://git.openjdk.java.net/jdk/pull/1524/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1524&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257448
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1524.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1524/head:pull/1524

PR: https://git.openjdk.java.net/jdk/pull/1524