This commit implements the workaround discussed in issue #686.

By default, bonded interfaces load balance the outgoing packets by
hashing only the MAC addresses. This commit changes this hash to
include the source and destination addresses of IPv4 and IPv6
headers as well.

Knowing the MAC addresses of all interfaces is useful to diagnose
issues in production; especially issues related to bonded interfaces.

Not only are the primary MAC addresses of the interfaces reported,
but also the secondary MAC addresses of the interfaces.

Waiting for links to come up is no longer helpful in the current
version of DPDK.

Having log entries reporting changes in the state of the links
eases diagnoses in production. This commit adds these log entries
through the Link State Change (LSC) interuption that most NICs
support. The information that a given NIC does not support
the LSC interuption is logged, but its link state is not monitored.

Since the callbacks of interuptions run in threads that are not
logical cores, this commit introduces the macro MAIN_LOG() to
Gatekeeper's log library to be used in these contexts.

If req_queue_init() fails before _all_ request queues are
initiated, sol_stage2() calls cleanup_sol(), which, in turn,
triggers a segmentation fault.

This commit solves this problem by adding list_initiated() to
include/list.h, and using it to test if the request queues are
initiated in cleanup_sol() before freeing the associated resources.

The original configuration of SOL blocks assumes that
the bandwidth of the back interface of a Gatekeeper server
is representative of the bandwidth of the destination network.
This assumption does not hold in production deployments of
Gatekeeper.  For example, Gatekeeper servers typically operate
in networks with higher speeds (e.g., 40Gbps) than the protected
destination (e.g., 10Gbps).

This commit introduces the parameter destination_bw_gbps to address
this reality.

This commit fixes two miscalculations in the size of mbuf pools:

1. calculate_mempool_config_para() was not accounting for
multiple members in bonded interfaces; and

2. Although unlikely, a GK or GT instance might receive all
the packets, so the instances must account for this worst case.