RFR: 8288140: Avoid redundant Hashtable.get call in Signal.handle

[Andrey Turbanov]

https://github.com/openjdk/jdk/blob/bc28baeba9360991e9b7575e1fbe178d873ccfc1/src/java.base/share/classes/jdk/internal/misc/Signal.java#L177-L178

Instead of separate Hashtable.get/remove calls we can just use value returned by `remove`,
It results in cleaner and a bit faster code.

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Commit messages:
 - [PATCH] Avoid redundant Hashtable.get call in Signal.handle
 - [PATCH] Avoid redundant Hashtable.get call in Signal.handle

Changes: https://git.openjdk.org/jdk/pull/9100/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9100&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288140
  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9100.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9100/head:pull/9100

PR: https://git.openjdk.org/jdk/pull/9100