org-export--get-subtree-options: Do not jump to parent subtree

* lisp/ox.el: Never jump to parent heading even when point is at an
existing heading.
* testing/lisp/test-ox.el (test-org-export/get-subtree-options): Fix
test assuming that current subtree may include parent.

Reported-by: Kaushal Modi <kaushal.modi@gmail.com>
Link: https://orgmode.org/list/CAFyQvY3mxi4DRTS+W-AX7bFELVujqH4DODEYPy3hyGRRuMEPSw@mail.gmail.com

lisp/ox.el

@@ -1435,7 +1435,7 @@ for export.  Return options as a plist."
   ;; property is the keyword with "EXPORT_" appended to it.
   (org-with-wide-buffer
    ;; Make sure point is at a heading.
-   (if (org-at-heading-p) (org-up-heading-safe) (org-back-to-heading t))
+   (org-back-to-heading t)
    (let ((plist
 	  ;; EXPORT_OPTIONS are parsed in a non-standard way.  Take
 	  ;; care of them right from the start.

testing/lisp/test-ox.el

@@ -391,7 +391,7 @@ Paragraph"
 	    (plist-get (org-export-get-environment nil t) :date))))
   ;; Still grab correct options when section above is empty.
   (should
-   (equal '("H1")
+   (equal '("H12")
 	  (org-test-with-temp-text "* H1\n** H11\n** H12<point>"
 	    (plist-get (org-export-get-environment nil t) :title))))
   ;; More than one property can refer to the same node property.