fix: rcmgr leak for downloader service

[joeylichang]

Description

1. Replicate background context by context with cancel, in defer will call cancel to close the connection.
2. Fixed the same problem in the put and sync object.
3. Polished the rcmgr related code and logs of the downloader and challenge.

Rationale

The client terminates requests during download, and memory statistics in the downloader service resource manager are not released. Because the gateway did not close the connection, the downloader service still did not release resources.

Example

N/A

Changes

Notable changes:

• gateway put/get object add context cancel
• gate sync object add context cancel

[sysvm]

LGTM