[gdb/testsuite] Fix gdb.base/break-probes.exp for remote target

With test-case gdb.base/break-probes.exp and target board
remote-gdbserver-on-localhost (using REMOTE_TARGET_USERNAME) we run into some
failures.

Fix these by adding the missing gdb_download_shlib and gdb_locate_shlib.

Tested on x86_64-linux.
1 file changed