## What changes were proposed in this pull request?

- update httpcore/httpclient to latest
- centralize version management
- remove excludes that are no longer relevant according to SBT/Maven dep graphs
- also manage httpmime to match httpclient

## How was this patch tested?

Jenkins tests, plus review of dependency graphs from SBT/Maven, and review of test-dependencies.sh  output

Author: Sean Owen <sowen@cloudera.com>

Closes #13049 from srowen/SPARK-12972.