When there is a connectivity problem between the server and the client (network outage, server crash or reboot), the client indefinitely hangs.

Trace:
 -> packet_write_wait(0xa8706c360, 0x0, 0x0, 0x0, 0x0, 0x600000)
   -> ssh_packet_write_wait(0xa870151e0, 0x0, 0x0, 0x0, 0x0, 0x600000)
     -> __addvdi3(0x4, 0x1, 0x0, 0x0, 0x0, 0x600000)
     <- __addvdi3() = 5
     -> ssh_packet_write_poll(0xa870151e0, 0x0, 0x0, 0x2dc, 0x8,
                              0x101010101010101)    
       -> sshbuf_len(0xa86ffc5d0, 0x0, 0x0, 0x2dc, 0x8, 
                     0x101010101010101)
       <- sshbuf_len() = 80
       -> sshbuf_ptr(0xa86ffc5d0, 0x0, 0x50, 0xf00, 0x8, 
                     0x101010101010101)
       <- sshbuf_ptr() = 0xa87070ae0
       -> roaming_write(0x4, 0xa87070ae0, 0x50, 0xffff80dc43363680, 0x8,
                        0x101010101010101)
 write(4, "1F {\004DB e iAC9399FA 8".., 80)      Err#32 EPIPE
     Received signal #13, SIGPIPE [ignored]
       <- roaming_write() = -1
     <- ssh_packet_write_poll() = 0xffffffe8 (SSH_ERR_SYSTEM_ERROR)
     -> sshbuf_len(0xa86ffc5d0, 0xa87070ae0, 0x20, 0x0, 0x8,
                   0x101010101010101)
     <- sshbuf_len() = 80
     -> __addvdi3(0x4, 0x1, 0x50, 0xf00, 0x8, 0x101010101010101)
     <- __addvdi3() = 5
     -> __addvdi3(0x4, 0x1, 0x10, 0x4, 0x8, 0x101010101010101)
     <- __addvdi3() = 5
 pollsys(0xFFFF80DC433635E0, 1, 0x00000000, 0x00000000) (sleep)

Here write fails with EPIPE, and roaming_write passes errno through.
ssh_packet_write_poll returns SSH_ERR_SYSTEM_ERROR.
But this error code is ignored in ssh_packet_write_wait.
Successive select on broken pipe hangs forever.

This looks to be a regression from 4509b5d4.
Pre 4509b5d4 EPIPE in ssh_packet_write_poll resulted in immediate fatal.
Post 4509b5d4 there is just one ignored error code.