RFR: 8282536: java.net.InetAddress should be a sealed class [v2]

[Aleksei Efimov]

> The following fix seals the `java.net.InetAddress` class and permits only two implementations - `java.net.Inet4Address` and `java.net.Inet6Address`. 
> 
> No issues have been detected by regression and JCK tests.
> 
> Links: [JBS](https://bugs.openjdk.java.net/browse/JDK-8282536) [CSR](https://bugs.openjdk.java.net/browse/JDK-8282880)

Aleksei Efimov has updated the pull request incrementally with one additional commit since the last revision:

  Cleanup unnessecary class loader checks, remove readObjectNoData

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7789/files
  - new: https://git.openjdk.java.net/jdk/pull/7789/files/2096e6b8..f6901f09

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7789&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7789&range=00-01

  Stats: 23 lines in 2 files changed: 0 ins; 21 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7789.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7789/head:pull/7789

PR: https://git.openjdk.java.net/jdk/pull/7789