bug#3957: split window for remote commands through eshell

Basically, any time a remote command gets executed through eshell, if
the frame is a single window it gets split into two windows.
Essentially, this is because tramp does its magic through
shell-command, which pops up a window if the output is too large to
fit in the minibuffer.

My first reaction was to wrap the relevant call to shell-command in a
save-window-excursion, but there seem to be some problems with that.
I'm currently trying to figure out how to prevent the root split, so
things like new frames are blocked as well.

It was suggested that I send the bug to this list so that a task would
be created that could be tracked.

Colin