Please review this fix for a regression in HttpExchange's setAttribute method.
The specification of setAttribute explicitly states that null values are allowed. JDK-8266897 changed `attributes` to `ConcurrentHashMap`, which does not allow null values. This patch modifies `setAttribute` to remove the attribute from the map when null value is requested. A new test was added to verify that setting attributes works as expected both for null and non-null values. Tier1-3 clean. ------------- Commit messages: - Fix null attribute handling Changes: https://git.openjdk.org/jdk/pull/13264/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13264&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8288109 Stats: 112 lines in 2 files changed: 111 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/13264.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/13264/head:pull/13264 PR: https://git.openjdk.org/jdk/pull/13264
