[IMP] allow cancel when sub request is in waiting state

easy_my_coop/views/subscription_request_view.xml

@@ -34,7 +34,7 @@
    				<header>
    					<button string="Validate" type="object" name="validate_subscription_request" attrs="{'invisible':['|',('state','not in',['draft','waiting']),('validated','=',False)]}"/>
    					<button string="Waiting list" type="object" name="put_on_waiting_list" states="draft"/>
-   					<button string="Cancel" type="object" name="cancel_subscription_request" states="draft,done,block" groups="easy_my_coop.group_easy_my_coop_user"/>
+   					<button string="Cancel" type="object" name="cancel_subscription_request" states="draft,waiting,done,block" groups="easy_my_coop.group_easy_my_coop_user"/>
    					<field name="state" widget="statusbar" statusbar_visible="draft,cancelled,done,failed"/>
    				</header>
    				<sheet>