RFR: 8271949: dumppath in -XX:FlightRecorderOptions does not affect

[Yasumasa Suenaga]

We set `dumppath` in `-XX:FlightRecorderOptions` or `JFR.configure dumppath` jcmd when we want to set emergency dump path. However they do not afffect.

### -XX:FlightRecorderOptions


$ java -XX:FlightRecorderOptions=dumppath=`pwd` -XX:StartFlightRecording -Xlog:exceptions=info --version
[0.032s][info][exceptions] Exception <a 'java/lang/IllegalArgumentException'{0x00000007470163b8}: Unknown argument 'dumppath' in diagnostic command.> (0x00000007470163b8)
thrown [open/src/hotspot/share/services/diagnosticFramework.cpp, line 215]
for thread 0x00007f4f700236a0
[0.033s][error][arguments ] Unknown argument 'dumppath' in diagnostic command.
Error occurred during initialization of VM
Failure when starting JFR on_create_vm_2


### jcmd

`jcmd` shows the configuration change was succeeded, but it would not affect.


$ jcmd 1046 JFR.configure dumppath=/tmp
1046:
Dump path: /tmp

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Commit messages:
 - 8271949: dumppath in -XX:FlightRecorderOptions does not affect

Changes: https://git.openjdk.java.net/jdk/pull/5019/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5019&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271949
  Stats: 93 lines in 8 files changed: 77 ins; 2 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5019.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5019/head:pull/5019

PR: https://git.openjdk.java.net/jdk/pull/5019