Infinity loop in synchronisation when priorities are higher than maximum in slave restart

[dcorbacho]

When pushing messages with a priority higher than the maximum, mirror node process(es) will crash when a slave node is restarted. That causes an infinity loop as synchronization is not able to finish.

=ERROR REPORT==== 12-May-2016::17:04:02 ===
** Generic server <0.30173.0> terminating  
** Last message in was {'$gen_cast',
                           {sync_start,#Ref<8977.0.524290.86024>,
                               <8977.24530.3>}}
** When Server state == {state,
                         {amqqueue,
                          {resource,<<"/">>,queue,<<"p_2">>},
                          true,false,none,
                          [{<<"x-max-priority">>,long,3}],
                          <8977.18865.3>,
                          [<0.30135.0>,<8978.24713.6>],
                          [],
                          ['rabbit@t-srv-rabbit06','rabbit@t-srv-rabbit05'],
                          [{vhost,<<"/">>},
                           {name,<<"ha.all">>},

.......
                         {dict,0,16,16,8,80,48,
                          {[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]},
                          {{[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]}}},
                         {dict,0,16,16,8,80,48,
                          {[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]},
                          {{[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]}}},
                         {state,
                          {dict,1,16,16,8,80,48,
                           {[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]},
                           {{[],[],[],[],[],[],[],[],[],[],[],[],[],[],
                             [[<8977.22136.3>|{delegate_12,<8977.22136.3>}]],
                             []}}},
                          delegate},
                         9462}
** Reason for termination ==
** {not_found,5}

Found while analyzing #687

[michaelklishin]

Nevermind my earlier comment, I now see a couple of recent comments in #687.