RFR: 8327182: Move serverAlias into the loop

[John Jiang]

In method `X509Authentication::createServerPossession`, it looks unnecessary to define variable `serverAlias` out of the for-loop.
It may be better to move `serverAlias` into that loop to narrow down the scope.

-------------

Commit messages:
 - 8327182: Move serverAlias into the loop

Changes: https://git.openjdk.org/jdk/pull/18100/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18100&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327182
  Stats: 3 lines in 1 file changed: 1 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18100.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18100/head:pull/18100

PR: https://git.openjdk.org/jdk/pull/18100