hg: jdk/sandbox: 8194154: System property user.dir should not be changed

[chris.hegarty at oracle.com]

Changeset: 847a988152b8
Author:    minqi
Date:      2018-02-21 14:23 -0800
URL:       http://hg.openjdk.java.net/jdk/sandbox/rev/847a988152b8

8194154: System property user.dir should not be changed
Summary: Cached user.dir so getCanonicalPath uses the cached value.
Reviewed-by: alanb, bpb, rriggs

! src/java.base/unix/classes/java/io/UnixFileSystem.java
! src/java.base/windows/classes/java/io/WinNTFileSystem.java
+ test/jdk/java/io/File/UserDirChangedTest.java