msgr: increment connect_seq when STANDBY->CONNECTING

msgr: increment connect_seq when STANDBY->CONNECTING

Otherwise we get this on the peer:

msg/SimpleMessenger.cc: In function 'int SimpleMessenger::Pipe::accept()':
msg/SimpleMessenger.cc:767: FAILED assert(existing->state == STATE_CONNECTING)
 1: (SimpleMessenger::Pipe::accept()+0x14b2) [0x654888]
 2: (SimpleMessenger::Pipe::reader()+0x32) [0x65538c]
 3: (SimpleMessenger::Pipe::Reader::entry()+0x19) [0x649493]
 4: (Thread::_entry_func(void*)+0x20) [0x659b06]
 5: /lib/libpthread.so.0 [0x7fcdc782f73a]
 6: (clone()+0x6d) [0x7fcdc6a5969d]
 NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this.