Revert partial NIO handling for Git hosting via HTTP

Bitbucket Server 7.0 includes changes to replacing blocking I/O for git processes with non-blocking I/O. However, NIO changes related to Git hosting via HTTP were only partially completed, and Git hosting via SSH was not updated at all.

To ensure consistent behavior, and to try and avoid any odd bugs related to the partially-completed NIO changes, the HTTP hosting changes should be reverted.