floss: Add socket connect command to btclient

Added a socket connect comand to btclient for testing. Also fixed
creating l2cap channels by switching back to classic l2cap instead of
using l2caple.

Bug: 241859545
Test: Create l2cap connection against bluez
Tag: #floss
Change-Id: Ice38fcc33c110580d6ddb9b2400d68c652f21bad