fix lf search bugs when no tag is on antenna

cotag read could enter endless loop, now cancels if the next bit doesn't
appear

em4x05 detection would loop due to a threshold never being met, now has
a dump out after 1000 samples tested.

fixed some indenting in hitag2 while i was reviewing that code for
potential endless loops...

client/cmdlfhitag.c

@@ -239,6 +239,7 @@ int CmdLFHitagReader(const char *Cmd) {
 	c.arg[0] = htf;
 
 	// Send the command to the proxmark
+	clearCommandBuffer();
 	SendCommand(&c);
 
 	UsbCommand resp;