Add serial console feature to seamicro driver

Implements a console driver -- "ShellinaboxConsole" -- that uses
telnet+shellinabox to connect to serial console of physical servers
configured within the Seamicro Fabric Compute system.

SeaMicro System provides telnet facility to connect to any of
it's physical server's serial console. Port to which we telnet
depends on server-id.

Change-Id: I2e60f6402a984dbbb6e0f749729c5a7006310076
Implements: blueprint seamicro-serial-console
Merge "Add serial console feature to seamicro driver"