[jdk13u-dev] RFR: 8062947: Fix exception message to correctly represent LDAP connection failure

[Alexey Bakhtin]

I'd like to backport JDK-8062947 to 13u as a follow-up of JDK-8160768.
Patch applies cleanly.
This patch is also required for clean backport of JDK-8245527

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Commit messages:
 - 8062947: Fix exception message to correctly represent LDAP connection failure

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/18/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=18&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8062947
  Stats: 246 lines in 3 files changed: 195 ins; 41 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/18.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/18/head:pull/18

PR: https://git.openjdk.java.net/jdk13u-dev/pull/18