RFR: 8335154: jcmd VM.classes -verbose=false does not set verbose to false

[Kevin Walls]

VM.classes uses:

995    VM_PrintClasses vmop(output(), _verbose.is_set());

_verbose.is_set() is wrong: it could be set, but set to false.

_verbose.value() should be used (see other examples such as StringtableDCmd::execute).

With this change -verbose=false will turn off verbose mode like all other DCmds which accept -verbose

bash-4.2$ jcmd 20193 VM.classes -verbose=false | wc -l
2490
bash-4.2$ jcmd 20193 VM.classes -verbose=true | wc -l
90258

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into ClassesDCmd_verbose
 - 8335154: jcmd VM.classes -verbose=false does not set verbose to false

Changes: https://git.openjdk.org/jdk/pull/19901/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19901&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335154
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19901.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19901/head:pull/19901

PR: https://git.openjdk.org/jdk/pull/19901