[mediacontroller] Use request_id for listener matching in SendCommand.

[mediacontroller] Use request_id for listener matching in SendCommand.

SendCommand method was using watchId to identify CommandReply callback which
should be called. It was passed in bundle object to mc_client_send_custom_cmd
function. Now instead of passing watchId we use already available request_id
to perform the same matching for command reply listeners.

[Verification]

Manual test.
tct-mediacontroller-tizen-tests - pass 100%

Change-Id: I57e90dbe36d7726f2e2f66866b11910d5d1d5d0d
Signed-off-by: Michal Michalski <m.michalski2@partner.samsung.com>