Fix gdb.mi/mi-breakpoint-changed.exp for remote targets

Fix gdb.mi/mi-breakpoint-changed.exp for remote targets

The libraries are never downloaded to the target for the first test
(test_insert_delete_modify), so the executable can't run properly.

I also added some with_test_prefix to help differentiate between the
different test case phases.

gdb/testsuite/ChangeLog:

	* gdb.mi/mi-breakpoint-changed.exp: Add some with_test_prefix.
	(test_insert_delete_modify): Call mi_load_shlibs before trying to
	run.