[jdk8u] RFR: 8290832: It is no longer possible to change "user.dir" in the JDK8

[Sergey Bylokhov]

This is the request to revert the fix for [JDK-8194154](https://bugs.openjdk.org/browse/JDK-8194154) integrated to the [openjdk8u342](https://github.com/openjdk/jdk8u/commit/5fcfb7acbe340c8347bd47413a36dd0b1e267dc1)

The fix for [JDK-8194154](https://bugs.openjdk.org/browse/JDK-8194154) disabled the possibility to change the "user.dir" property.
Changing the "user.dir" was not recommended from the beginning but it was not forbidden, so there are some old applications that rely on the old behavior. 

For compatibility reasons, it would be good to restore the old behavior.

This PR reverts this commit: https://github.com/openjdk/jdk8u/commit/5fcfb7acbe340c8347bd47413a36dd0b1e267dc1

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Commit messages:
 - Revert "8194154: System property user.dir should not be changed"

Changes: https://git.openjdk.org/jdk8u/pull/14/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u&pr=14&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290832
  Stats: 67 lines in 3 files changed: 0 ins; 65 del; 2 mod
  Patch: https://git.openjdk.org/jdk8u/pull/14.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u pull/14/head:pull/14

PR: https://git.openjdk.org/jdk8u/pull/14