Override getThreadPool from HystrixConcurrencyStrategy and delegate to

existing strategy if present. Fixes #2035

This allows clients to send batched up events in the same format as
before (or to continue to send single events). We can switch the
default format to an array in 1.4.x.

fixes a problem with whitespaces in list of retryable status codes

Merge branch 'fix_whitespaces_in_retryable_status_codes_list' of github.com:doernbrackandre/spring-cloud-netflix into fix_whitespaces_in_retryable_status_codes_list

This reverts commit f5524263.

Close response when retry on certain status codes

fixes gh-2028

Previously, these were managed directly via archaius, but due to
some combination of changes in boot 1.5.x (likely a tomcat change as
zuul filters were initialzed in a servlet context listener) and Dalston,
The filter was created before archaius could be initialized.

The properties are backwards compatible and are in the
`ZuulProperties.Host` object.

fixes gh-1950

use only default https ports for https check

Deprecates RetryableStatusCodeException