testsuite: Update py-mi-objfile to expect console format print

testsuite: Update py-mi-objfile to expect console format print

Starting with this commit:

  commit e7ea3ec7c623be0b9be1eaf4929794652a84be11
  Author: Catalin Udma <catalin.udma@freescale.com>
  Date:   Mon Feb 29 16:16:19 2016 +0200

    python: Use console format for output of gdb.execute command

the python script would use console format for gdb.execute output.
This patch fixes py-mi-objfile to expect the console format when is
checking for gdb.execute printing.

gdb/testsuite/ChangeLog:
2016-04-05  Catalin Udma  <catalin.udma@freescale.com>

        * gdb.python/py-mi-objfile-gdb.py: Use "list main" command.
        * gdb.python/py-mi-objfile.exp: Match "list main" output
        in console format.

Signed-off-by: Catalin Udma <catalin.udma@freescale.com>