Shutdown hang on 16.04 with iscsi targets

I have 4 servers running the latest 16.04 updates from the development branch (as of right now).

Each server is connected to NetApp storage using iscsi software initiator. There are a total of 56 volumes spread across two NetApp arrays. Each volume has 4 paths available to it which are being managed by device mapper.

While logged into the iscsi sessions all I have to do is reboot the server and I get a hang.

I see a message that says:

  "Reached target Shutdown"

followed by

  "systemd-shutdown[1]: Failed to finalize DM devices, ignoring"

and then I see 8 lines that say:

  "connection1:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection2:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection3:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection4:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection5:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection6:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection7:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  "connection8:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
  NOTE: the actual values of the *'s differ for each line above.

This seems like a bug somewhere but I am unaware of any additional logging that I could turn on to pinpoint the problem.

Note I also have similar setups that are not doing iscsi and they don't have this problem.

Should this get posted as a bug?