RFR: 8293326: jdk/sun/security/tools/jarsigner/compatibility/SignTwice.java slow on Windows

[Daniel Jeliński]

This patch enables SignTwice test to complete faster on Windows machines.

The test starts `keytool` and `jarsigner` a number of times, passing `-J-Djava.security.egd=file:/dev/./urandom` to the started process, presumably to avoid blocking on VMs with insufficient entropy. This works fine on machines where `/dev/./urandom` is actually present. On Windows it makes the JVM use `ThreadedSeedGenerator`, which is very slow compared to the other options.

The fix removes `java.security.egd` setting on Windows machines.

Alternatively we could change the egd to use `file:/dev/urandom` (without the `/./` part); this also fixes the Windows problem. Is the `/./` part still needed? If I understand correctly, it was a workaround for some JDK7 bug.

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Commit messages:
 - Remove dev/./urandom on Windows

Changes: https://git.openjdk.org/jdk/pull/10160/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10160&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293326
  Stats: 13 lines in 1 file changed: 10 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10160.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10160/head:pull/10160

PR: https://git.openjdk.org/jdk/pull/10160