Run a shell in the allocated node with salloc

By default, salloc will open a new shell in the *current* node instead
of in the allocated node. This often causes users to leave the extra
shell running once the allocation ends. Repeating this process several
times causes chains of shells.

By running the shell in the remote node, once the allocation ends the
shell finishes as well.

Fixes: #174
See: https://slurm.schedmd.com/faq.html#prompt

m/module/slurm-common.nix

@@ -86,8 +86,6 @@ in {
       # when a task runs (srun) so we can ssh early.
       PrologFlags=Alloc,Contain,X11
 
-      # LaunchParameters=ulimit_pam_adopt will set RLIMIT_RSS in processes
-      # adopted by the external step, similar to tasks running in regular steps
       LaunchParameters=use_interactive_step
       SlurmdDebug=debug5
       #DebugFlags=Protocol,Cgroup