Fix error when splicing Eshell globs and a glob expands to itself

Fix error when splicing Eshell globs and a glob expands to itself

This could happen when 'eshell-extended-glob' determines that a "glob"
is not really a glob.  This mainly happens for remote file names with a
"~" in them, like "/ssh:remote:~/file.txt".

* lisp/eshell/em-glob.el (eshell-extended-glob): Return a list when
'eshell-glob-splice-results' is non-nil.
* test/lisp/eshell/em-glob-tests.el
(em-glob-test/expand/splice-results)
em-glob-test/expand/no-splice-results): Extend tests.