Replace DMTCP_HOST/PORT with DMTCP_COORD_HOST/PORT about dmtcp

[gc00]

Good point! I assume we keep -h and -p. Should we have three synonymous flags and two environment variables temporarily for backward compatibitity?
-h --host --coord-host
DMTCP_HOST DMTCP_COORD_HOST
and the same for ports?
I'll volunteer to create the pull request. Is that the right spec? (In a future release, we can remove DMTCP_HOST and DMTCP_PORT, but we'll keep it for DMTCP 2.4.0.)

[gc00]

For testing, we'll need to test for dmtcp_launch --no-coordinator, as well as dmtcp_launch -p0, and the combination of the two. Similarly, need to test for dmtcp_restart -p0, and we need to test dmtcp_coordinator and dmtcp_command. Note also that what DMTCP does with DMTCP_HOST/PORT environment variables currently is rather haphazard. Also, after dmtcp_restart --port XX, when we call mtcp_restart, we revert back to the previous environment variables or information in the SharedData area.
We also need to test for dmtcp_launch -p0 --port-file MYFILE (and without -p0).

[gc00]

This issue has now been fixed by pull request #92.

However, notice that issue #93 has now been opened, due to a related issue that affects dmtcp_restart saving the old pre-ckpt DMTCP_COORD_PORT in its memory, and then using the old value to re-connect to the coordinator in cases where the socket temporarily breaks. This doesn't work if there is a new coordinator on a different port after restart.