fix layout of password protected shares

* add password icon
* fix upshifted arrow button - fixes #9024

apps/files_sharing/css/authenticate.css

@@ -14,3 +14,11 @@ input[type='submit'] {
 	position: absolute;
 	top: 0px;
 }
+
+fieldset > p {
+	position: relative;
+}
+
+#password-icon {
+	top: 20px;
+}

apps/files_sharing/templates/authenticate.php

@@ -12,6 +12,7 @@
 				placeholder="<?php p($l->t('Password')); ?>" value=""
 				autocomplete="off" autocapitalize="off" autocorrect="off"
 				autofocus />
+			<img class="svg" id="password-icon" src="/master/core/img/actions/password.svg" alt="">
 			<input type="submit" value="" class="svg icon-confirm" />
 		</p>
 	</fieldset>