Add RequestJob wrapper to preserve VCAP-Request-ID on async jobs

* Modified Jobs::Enqueuer to wrap all jobs in RequestJob.

[#63557568]

Signed-off-by: Karl Isenberg <kisenberg@pivotallabs.com>
Move Steno request_guid into VCAP::Request.current_id setter

[#63557568]

Signed-off-by: Eric Malm <emalm@pivotallabs.com>
Add logging to all async jobs; fix thread-scoped request_guid test pollution

[#63557568]

Signed-off-by: Eric Malm <emalm@pivotallabs.com>
Fix Steno test pollution from re-initialization

* Insulate request_spec.rb againt Null steno context.
* Change spec helper Steno log level to debug2 from info.

[#63557568]

Signed-off-by: Karl Isenberg <kisenberg@pivotallabs.com>
Add StenoConfigurer helper for consistent Steno configuration

* StenoConfigurer calls Steno.init with a Steno::Config derived from
the logging config hash provided. Its #configure method ensures that
a ThreadLocal Steno::Context is provided by default and optionally
takes a block that allows modification of the hash to be passed into
Steno::Config.new.

[#63557568]

Signed-off-by: Karl Isenberg <kisenberg@pivotallabs.com>