gdb/testsuite: adjust another add-inferior test for native-extended-gdbserver board

I see this FAIL when running with the native-extended-gdbserver board:

    Expecting: ^(-add-inferior[^M
    ]+)?(.*\^done,inferior="i2"[^M
    ]+[(]gdb[)] ^M
    [ ]*)
    -add-inferior^M
    =thread-group-added,id="i2"^M
    ~"[New inferior 2]\n"^M
    ~"Added inferior 2 on connection 1 (extended-remote localhost:2345)\n"^M
    ^done,inferior="i2",connection={number="1",name="extended-remote"}^M
    (gdb) ^M
    FAIL: gdb.mi/set-show.exp: test_per_inferior_parameters: add inferior (unexpected output)

This is another case of the add-inferior command producing more output
when connected to a remote target.  Adjust the regexp to accomodate it.

Change-Id: Ifa0590211fd75d4a01dff942c6bb810d5caf1257
1 file changed