[jdk15u-dev] RFR: 8261534: Test sun/security/pkcs11/KeyAgreement/IllegalPackageAccess.java fails on platforms where no nsslib artifacts are defined

[Evgeny Astigeevich]

[JDK-8259319](https://bugs.openjdk.java.net/browse/JDK-8259319) was backported to 15u. As we see the test failing, we need to backport this testfix to 15u as well. Patch applies cleanly. No risk, testfix only.
Tested:
- `make run-test TEST=sun/security/pkcs11/KeyAgreement/IllegalPackageAccess.java`: Passed

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Commit messages:
 - Backport dc46aa85c6e16cb904d1c40a4577b5e48c56a3d4

Changes: https://git.openjdk.java.net/jdk15u-dev/pull/182/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk15u-dev&pr=182&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261534
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk15u-dev/pull/182.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk15u-dev pull/182/head:pull/182

PR: https://git.openjdk.java.net/jdk15u-dev/pull/182