RFR: 8266770: Clean pending exception before running dynamic CDS dump

[Yumin Qi]

Hi, 
  The change is simple for reorder the exception cleaning in JavaThread::invoke_shutdown_hooks:
   We should clean the pending exception before calling into  MetaspaceShared::link_and_cleanup_shared_classes at dynamic dump, or it will cause it fail.

   Tests: tier1,tier2,tier3,tier4

  Thanks
  Yumin

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Commit messages:
 - 8266770: Clean pending exception before running dynamic CDS dump

Changes: https://git.openjdk.java.net/jdk/pull/3978/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3978&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266770
  Stats: 12 lines in 1 file changed: 7 ins; 5 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3978.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3978/head:pull/3978

PR: https://git.openjdk.java.net/jdk/pull/3978