step-over-trips-on-watchpoint.exp: Don't put addresses in test messages

step-over-trips-on-watchpoint.exp: Don't put addresses in test messages

Diffing test results, I noticed:

 -PASS: gdb.threads/step-over-trips-on-watchpoint.exp: displaced=on: with thread-specific bp: next: b *0x0000000000400811 thread 1
 +PASS: gdb.threads/step-over-trips-on-watchpoint.exp: displaced=on: with thread-specific bp: next: b *0x00000000004007d1 thread 1

gdb/testsuite/ChangeLog:
2015-04-10  Pedro Alves  <palves@redhat.com>

	* gdb.threads/step-over-trips-on-watchpoint.exp (do_test): Use
	test messages that don't include the breakpoint address.