RFR: 8303832: Use enhanced-for cycle instead of Enumeration in JceKeyStore

[Andrey Turbanov]

java.util.Enumeration is a legacy interface from java 1.0.
There is couple of places with cycles which use it to iterate over collections. We can replace this manual cycle with enchanced-for, which is shorter and easier to read.

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Commit messages:
 - [PATCH] Use enhanced-for cycle instead of Enumeration in JceKeyStore

Changes: https://git.openjdk.org/jdk/pull/12930/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12930&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303832
  Stats: 8 lines in 1 file changed: 0 ins; 5 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12930.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12930/head:pull/12930

PR: https://git.openjdk.org/jdk/pull/12930