RFR: JDK-8282686: Add constructors taking a cause to SocketException [v3]

[Joe Darcy]

> Please review this small API enhancement to add the usual constructors taking a cause to SocketException and then update uses of initiCause on creating SocketException to instead pass the cause via the constructor.
> 
> Please also review the CSR: https://bugs.openjdk.java.net/browse/JDK-8282688

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Improve test.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7705/files
  - new: https://git.openjdk.java.net/jdk/pull/7705/files/978b379d..da863692

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7705&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7705&range=01-02

  Stats: 11 lines in 1 file changed: 8 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7705.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7705/head:pull/7705

PR: https://git.openjdk.java.net/jdk/pull/7705