RFR: 7480: Trim method descriptor value

[Gunnar Morling]

Hey @thegreystone, here's a fix for trimming the method signature value when building the method descriptors in the agent. Without this, wrapping the tags around long signatures like that [will fail](https://github.com/moditect/jfrunit-examples/commit/bd4bc8023c760a3d719dc9295cbe010fb56d7f6f#diff-8999381a163c84127b7e94462f39060c054a984904f82c34713d0ade0954e4c5R81):


 <descriptor>
   (Ljava/sql/PreparedStatement;Ljava/lang/Object;ILorg/hibernate/type/descriptor/WrapperOptions;)V
</descriptor>


Could you log an issue if you think it's a worthwhile fix? The second commit is some unrelated clean-up I did along the way. Thx!

-------------

Commit messages:
 - 9999: Removing unused import and local var
 - 9999: Trimming descriptor

Changes: https://git.openjdk.java.net/jmc/pull/343/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=343&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7480
  Stats: 3 lines in 2 files changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/jmc/pull/343.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/343/head:pull/343

PR: https://git.openjdk.java.net/jmc/pull/343