tests: Bluetooth: Classic: rfcomm_s: Check connect event before send

Sometimes, the command `rfcomm_s send 9 1` will fail to execute due
to the DLC has not been established.

Check the DLC connected event before sending shell command
`rfcomm_s send 9 1`.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>
1 file changed