OFStateManager: remove redundant logs
OFConnectionManager: use cxn_ip_string in message traces
OFConnectionManager: create API for indigo_cxn_send_async_message

This function was previously invoked by passing UNSPECIFIED as the cxn id.
OFStateManager: remove unused cxn_id param from ind_core_flow_entry_delete
OFStateManager: remove ind_core_xid_alloc

Flow-removed messages don't need XIDs.
OFStateManager: get flow-removed msg version from OFConnectionManager
OFStateManager: remove unused ft_delete_id
OFStateManager: ft_delete cannot fail
OFStateManager: cleanup ind_core_port_mod_handler
OFStateManager: fix bug in utest
add style guide

Copied from an older repository.