patch 9.1.1295: clientserver: does not handle :stopinsert correctly

Problem:  clientserver: When in insert mode, a :stopinsert command
          is not correctly processed (user202729)
Solution: If the :stopinsert command is received while waiting for
          input, stuff the NOP key into the type-ahead buffer and
          detect that :stopinsert was used in edit() so that the
          cursor position is decremented.

fixes: #17016
closes: #17024

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/ex_docmd.c

@@ -9326,6 +9326,12 @@ ex_stopinsert(exarg_T *eap UNUSED)
 {
     restart_edit = 0;
     stop_insert_mode = TRUE;
+#if defined(FEAT_CLIENTSERVER) || defined(FEAT_EVAL)
+    // when called from remote_expr in insert mode, make sure insert mode is
+    // ended by adding K_NOP to the typeahead buffer
+    if (vgetc_busy)
+       ins_char_typebuf(K_NOP, 0);
+#endif
     clearmode();
 }