Start fixing tramp completion user-error for emacs-24.4.

* helm-files.el (helm-find-files-get-candidates): let-bind non-essential
* helm-utils.el: Comment tramp-dissect-file-name defadvice.
* helm.el: let-bind non-essential to t on helm startup.

helm-files.el

@@ -1322,6 +1322,7 @@ purpose."
                             (file-name-as-directory path)
                             (file-name-directory path)))
          invalid-basedir
+         non-essential
          (tramp-verbose helm-tramp-verbose)) ; No tramp message when 0.
     (set-text-properties 0 (length path) nil path)
     ;; Issue #118 allow creation of newdir+newfile.

helm-utils.el

@@ -175,12 +175,12 @@ Return nil if DIR is not an existing directory."
                   concat (if p (concat "/" i) (concat i "/")) into root
                   finally return (file-equal-p (file-truename root) f2)))))))
 
-(when (and (require 'tramp)
-           (fboundp 'tramp-compat-user-error))
-  (defadvice tramp-dissect-file-name (around disable-user-error activate)
-    "Disable `user-error'."
-    (flet ((tramp-compat-user-error (format &rest objects) nil))
-      ad-do-it)))
+;; (when (and (require 'tramp)
+;;            (fboundp 'tramp-compat-user-error))
+;;   (defadvice tramp-dissect-file-name (around disable-user-error activate)
+;;     "Disable `user-error'."
+;;     (flet ((tramp-compat-user-error (format &rest objects) nil))
+;;       ad-do-it)))
 
 
 ;; CUA workaround

helm.el

@@ -1479,6 +1479,7 @@ ANY-KEYMAP ANY-DEFAULT ANY-HISTORY See `helm'."
           ;; #163 no cursor in minibuffer in <=Emacs-24.2.
           ;; This is not needed in emacs-24.3+
           (cursor-in-echo-area t)
+          (non-essential t)
           (helm-maybe-use-default-as-input
            (or helm-maybe-use-default-as-input ; it is let-bounded so use it.
                (loop for s in (helm-normalize-sources any-sources)