Override server SCSS rules for confirm button in guest pages

As the server defines some SCSS rules using "XXX + .icon-confirm" the
selector is more specific than just "input" used in "guest.css", so
the server SCSS rules took precedence over the guest CSS rules. Now a
more specific selector was added to the guest and public share auth
rules; as the guest and public share auth rules are loaded after the
server ones now the guest rules for input elements take precedence over
the server ones.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

core/css/guest.css

@@ -176,6 +176,7 @@ input:not([type='range']) {
 	-webkit-appearance: none;
 }
 input[type='submit'],
+input[type='submit'].icon-confirm,
 input[type='button'],
 button, .button,
 select {
@@ -208,6 +209,7 @@ input.login {
 	background-position: right 16px center;
 }
 input[type='submit'],
+input[type='submit'].icon-confirm,
 input.updateButton,
 input.update-continue {
 	padding: 10px 20px; /* larger log in and installation buttons */

core/css/publicshareauth.css

@@ -14,7 +14,8 @@ form fieldset {
 	min-width: 0; /* FF hack for to override default value */
 }
 
-input[type='submit'] {
+input[type='submit'],
+input[type='submit'].icon-confirm {
 	width: 45px;
 	height: 45px;
 	margin-left: 0 !important;