RFR: 8253155: Minor cleanups and Javadoc fixes for LdapDnsProvider of java.naming

[Christoph Langer]

There are some little flaws in LdapDNSProvider and auxilliary classes, mostly in Javadoc.

In detail:
src/java.naming/share/classes/com/sun/jndi/ldap/DefaultLdapDnsProvider.java: Unnecessary import
src/java.naming/share/classes/com/sun/jndi/ldap/LdapDnsProviderService.java: typo
src/java.naming/share/classes/javax/naming/ldap/spi/LdapDnsProvider.java: Whitespace
src/java.naming/share/classes/javax/naming/ldap/spi/LdapDnsProviderResult.java: Spelling of "ldap" -> should be
capitalized

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Commit messages:
 - JDK-8253155

Changes: https://git.openjdk.java.net/jdk/pull/168/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=168&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253155
  Stats: 21 lines in 4 files changed: 3 ins; 7 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/168.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/168/head:pull/168

PR: https://git.openjdk.java.net/jdk/pull/168