KNOX-2897 - Using Expect:100-continue wherever possible to upload big content

[smolnar82]

What changes were proposed in this pull request?

This commit consists of the following changes:

• the new-style "Expect:100-continue" approach for PUT/POST requests is disabled by default
• the new-style "Expect:100-continue" approach is enabled for the ATLAS, ATLAS-API, HIVE, RANGER and RANGER-UI services
• make sure that this feature for the WEBHDFS service is turned off even in its own service definition file (so that if the default is changed back to true, we'll be safe)
• HTTP entity creation relies on the 'addExpect100Continue' boolean flag
• implemented the missing method overload in HdfsHttpClientDispatch
• KnoxBufferedHttpEntity shall not read content at entity creation time (content reading is postponed until dispatch time when the back-end service actually needs the data)

How was this patch tested?

Manual testing on a live cluster with the affected services (ATLAS, HIVE, RANGER)