Prefer defvar-keymap in net/*.el

Prefer defvar-keymap in net/*.el

* lisp/net/dictionary.el (dictionary-mode-map):
* lisp/net/dig.el (dig-mode-map):
* lisp/net/eudc-hotlist.el (eudc-hotlist-mode-map):
* lisp/net/eudc.el (eudc-mode-map):
* lisp/net/mairix.el (mairix-searches-mode-map):
* lisp/net/newst-treeview.el
(newsticker-treeview-list-sort-button-map)
(newsticker-treeview-mode-map):
* lisp/net/quickurl.el (quickurl-list-mode-map):
* lisp/net/rcirc.el (rcirc-mode-map)
(rcirc-multiline-minor-mode-map, rcirc-track-minor-mode-map):
* lisp/net/rlogin.el (rlogin-mode-map):
* lisp/net/secrets.el (secrets-mode-map):
* lisp/net/sieve-mode.el (sieve-mode-map):
* lisp/net/sieve.el (sieve-manage-mode-map):
* lisp/net/snmp-mode.el (snmp-mode-map):
* lisp/net/telnet.el (telnet-mode-map): Prefer defvar-keymap.