fix some iclass reader bugs (#350)

endless loop in reader if no tag was found
button press on pm3 did not cancel.
led_b was left on in some cases
also moved 14b detection to last in hf search to help speed up the
command for the other tags.  14b is slow (does multiple tests)
Thanks to @Fl0-0 and @pwpiwi for their idenfication of some of the
issues.