RFR: 8329213: Better validation for com.sun.security.ocsp.useget option

[Aleksey Shipilev]

[JDK-8328638](https://bugs.openjdk.org/browse/JDK-8328638) introduced a new boolean option, `com.sun.security.ocsp.useget`. We use the usual `Boolean.parseBoolean` to convert it from String to boolean value, which works correctly for `false` and `true` as boolean values. However, any string that is not `true` would be treated as `false`. Which means that if users mistype the value, they would get a `false`, which is a non-default value, which is against the spirit of the JDK-8328638.

It would be preferable to validate the option range a bit better, and default to the correct value on any error.

Additional testing:
  - [x] Eyeballing `GetAndPostTests` debugging, checking that GET/POST are properly enabled/disabled for `false`, `true`, `foobar` passed as option values
  - [x] `jdk_security`, out of the box
  - [x] `jdk_security` with `-Dcom.sun.security.ocsp.useget=false` passes
  - [x] `jdk_security` with `-Dcom.sun.security.ocsp.useget=foobar` passes

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/18525/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18525&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329213
  Stats: 37 lines in 2 files changed: 33 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/18525.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18525/head:pull/18525

PR: https://git.openjdk.org/jdk/pull/18525