[binutils-gdb] Change captured_mi_execute_command to use scoped_restore

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 789c4b5ea14b0c441e6021f07503e61ccfacb427 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: 789c4b5ea14b0c441e6021f07503e61ccfacb427

Change captured_mi_execute_command to use scoped_restore

Change captured_mi_execute_command to use a scoped_restore, removing a
cleanup.  The old code copied the current token, but I don't believe
that is necessary.

gdb/ChangeLog
2017-09-29  Tom Tromey  <tom@tromey.com>

	* mi/mi-main.c (captured_mi_execute_command): Use scope_restore.