src: only commit stickydisk in post step if in setup-only

Firstly this was a bug where we were trying to commit in the post
step even if we had already committed at the end of the main step in
a non-setup-only invocation.

Secondly, if the action is canceled before the exposeID is set in the main
process, we don't want to send a commit request with an empty exposeID.

src/state-helper.ts

@@ -65,4 +65,12 @@ export function setExposeId(exposeId: string) {
 
 export function getExposeId(): string {
   return core.getState('exposeId');
-}
+}
+
+export function setSetupOnly(setupOnly: boolean) {
+  core.saveState('setupOnly', setupOnly.toString());
+}
+
+export function getSetupOnly(): boolean {
+  return core.getState('setupOnly') === 'true';
+}