Warn if serf events have queued up past 80% of the limit
Warn if serf events have queued up past 80% of the limit

It is theoretically possible that the number of queued serf events can back up.  If this happens, emit a warning message if there are more than 200 events in queue.

Most notably, this can happen if `c.consulServerLock` is held for an "extended period of time".  The probability of anyone ever seeing this log message is hopefully low to nonexistent, but if it happens, the warning message indicating a large number of serf events fired while a lock was held is likely to be helpful (vs serf mysteriously blocking when attempting to add an event to a channel).

pmalmgren/consul,mckennajones/consul,sean-/consul,calgaryscientific/consul,sequenceiq/consul,sean-/consul,pmalmgren/consul,mshean/consul,mckennajones/consul,andygoalkeeper/consul,i0rek/consul,samaitra/consul,Thib17/consul,Pivotal-Pierre-Delagrave/consul,youhong316/consul,andygoalkeeper/consul,kaskavalci/consul,mshean/consul,kylemcc/consul,tshak/consul,sunadm/consul,42wim/consul,kylemcc/consul,tugbabodrumlu/consul,sunadm/consul,andygoalkeeper/consul,Thib17/consul,zeroae/consul,jovandeginste/consul,zeroae/consul,leowmjw/consul,rhyas/consul,Thib17/consul,kaskavalci/consul,youhong316/consul,i0rek/consul,vamage/consul,vamage/consul,i0rek/consul,tshak/consul,kingland/consul,samaitra/consul,Pivotal-Pierre-Delagrave/consul,lindenlab/consul,andygoalkeeper/consul,pmalmgren/consul,leowmjw/consul,sequenceiq/consul,hashicorp/consul,scalp42/consul,tshak/consul,scalp42/consul,tugbabodrumlu/consul,sequenceiq/consul,kingland/consul,sunadm/consul,sunadm/consul,rhyas/consul,scalp42/consul,zeroae/consul,42wim/consul,rhyas/consul,jovandeginste/consul,scalp42/consul,kingland/consul,sweeneyb/consul,Thib17/consul,lindenlab/consul,sequenceiq/consul,calgaryscientific/consul,sweeneyb/consul,sean-/consul,tshak/consul,sweeneyb/consul,tugbabodrumlu/consul,calgaryscientific/consul,i0rek/consul,dankraw/consul,42wim/consul,mshean/consul,andygoalkeeper/consul,vamage/consul,jovandeginste/consul,dankraw/consul,hashicorp/consul,pmalmgren/consul,youhong316/consul,vamage/consul,youhong316/consul,mckennajones/consul,Thib17/consul,sean-/consul,youhong316/consul,sunadm/consul,kylemcc/consul,calgaryscientific/consul,jovandeginste/consul,kaskavalci/consul,kaskavalci/consul,Pivotal-Pierre-Delagrave/consul,hashicorp/consul,leowmjw/consul,samaitra/consul,lindenlab/consul,scalp42/consul,mckennajones/consul,sweeneyb/consul,samaitra/consul,Pivotal-Pierre-Delagrave/consul,lindenlab/consul,jovandeginste/consul,Pivotal-Pierre-Delagrave/consul,tugbabodrumlu/consul,lindenlab/consul,tshak/consul,sean-/consul,sequenceiq/consul,kingland/consul,samaitra/consul,zeroae/consul,zeroae/consul,hashicorp/consul,mshean/consul,tugbabodrumlu/consul,mshean/consul,kylemcc/consul,sweeneyb/consul,pmalmgren/consul,calgaryscientific/consul,kaskavalci/consul,vamage/consul,dankraw/consul,rhyas/consul,mckennajones/consul,dankraw/consul,42wim/consul,rhyas/consul,leowmjw/consul,i0rek/consul,leowmjw/consul,kingland/consul,dankraw/consul,42wim/consul,kylemcc/consul