Fixing sending of abort-multipart-upload message

Fixing abort-multipart-upload message not being sent during a canceled or failed multipart upload.

Fixing Signing Bug

Turning off path normalization for default signing config as this can cause a signing mismatch with the service.

Fixing bug that could cause a slow-down/hang

Fixing bug with prepared request counter that could cause a slow-down or hang.

Changes for Custom Headers/Query Parameters

• Adding exclusion lists for headers when deriving messages to keep custom headers.
• Fixing query parameters bug where deriving messages from a message with existing query parameters could generate an incorrect query parameters string.

Max connections override

Added max connections override for capping the amount of active client connections.

Improving request flow

Request preparation (ie: signing, reading from a stream, etc.) will now happen in a different ELG from the network IO ELG.

User-Agent Changes

• Adding user-agent information about the client to request headers.

Bug Fixes

• Fixing bug with num_active_vip_connections counter
• Fixing two race conditions related to client clean up

Logging Changes

• Additional logging and removing toggle for client stats logging.

New managed thread API

Convert to new managed thread system for threads that cannot be reliably explicitly joined.