RFR: 8265915: adjust state_unloading_cycle compuation order in nmethod::is_unloading

[Miao Zheng]

Trivial change of moving state_unloading_cycle computation after state_is_unloading checking. Avoiding useless state_unloading_cycle computation when state_is_unloading is true.

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Commit messages:
 - 8265915: adjust state_unloading_cycle compuation order in nmethod::is_unloading

Changes: https://git.openjdk.java.net/jdk/pull/3676/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3676&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265915
  Stats: 2 lines in 1 file changed: 1 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3676.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3676/head:pull/3676

PR: https://git.openjdk.java.net/jdk/pull/3676