gdb.base/bp-permanent.exp: Tighten regex

gdb.base/bp-permanent.exp: Tighten regex

Trying to fix a permanent breakpoints bug, I broke "next" over a
regular breakpoint.  "next" would immediately hit the breakpoint the
program was already stopped at.  But, the "next over setup" test
failed to notice this and still issued a pass.  That's because the
regex matches "testsuite" in:

  Breakpoint 2 at 0x400687: file src/gdb/testsuite/gdb.base/bp-permanent.c, line 46.

gdb/testsuite/ChangeLog:
2015-03-05  Pedro Alves  <palves@redhat.com>

	* gdb.base/bp-permanent.exp: Tighten "next over setup" regex.