RSE: Drop the comms link once session is closed

Drop the communication link before resuming system execution. As per the
ADAC spec, above step is performed after response is sent to the client.

Also only perform this step when the close session command response is
successfully sent to the client.

Signed-off-by: Maulik Patel <maulik.patel@arm.com>
Change-Id: I0b16e8a59ba735ffff350a77b4c42259c24406f7
12 files changed