Don't handle timeout inside gdb_test_multiple

Don't handle timeout inside gdb_test_multiple

This fixes a few cases where the testcase is explicitly handling timeouts
inside gdb_test_multiple when it is not necessary.

It also converts two gdb_test_multiple calls to gdb_test_no_output calls
(also removing the timeout handling).

gdb/testsuite/ChangeLog:

2016-12-01  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.base/maint.exp: Remove timeout handling for gdb_test_multiple.
	* gdb.cp/gdb2495.exp: Likewise and convert gdb_test_multiple into
	gdb_test_no_output for a couple of cases.
	* gdb.cp/ovldbreak.exp: Remove timeout handling for gdb_test_multiple.