CLI: Remove calls to ast_cli_generator.

The ability to add to localized storage cannot be supported by
ast_cli_generator.  The only calls to ast_cli_generator should be by
functions that need to proxy the CLI generator, for example 'cli check
permissions' or 'core show help'.

* ast_cli_generatornummatches now retrieves the vector of matches and
  reports the number of elements (not including 'best' match).
* test_substitution retrieves and iterates the vector.

Change-Id: I8cd6b93905363cf7a33a2d2b0e2a8f8446d9f248

include/asterisk/cli.h

@@ -287,6 +287,9 @@ int ast_cli_unregister_multiple(struct ast_cli_entry *e, int len);
  * Useful for readline, that's about it
  * \retval 0 on success
  * \retval -1 on failure
+ *
+ * Only call this function to proxy the CLI generator to
+ * another.
  */
 char *ast_cli_generator(const char *, const char *, int);