Tweak needle matches at start of _do_install_and_reboot
    
    The way this was set up before, if `anaconda_main_hub` matched
    immediately but some spoke was still in a 'processing' state,
    it only had 30 seconds (default `assert_and_click` timeout) to
    complete and allow the 'Begin Installation' button to appear.
    It seems unnecessary to match on *both* needles, really, so
    let's just give 300 seconds for the `begin_installation` needle
    to appear. It's not going to appear on any other screen.
    
    This problem caused a couple of spurious failures today -
    https://openqa.fedoraproject.org/tests/77839 and
    https://openqa.fedoraproject.org/tests/77858 - because they
    took a bit too long for the INSTALLATION DESTINATION spoke to
    clear.