nfc_initiator_target_is_present() makes PN533 unusable after some -4A cards

Diagnose is used behind the hood with -4A cards.
But after using it on some cards, it's not possible to detect the reader 
anymore until re-plugged.

Example:

$ pn53x-tamashell 
NFC reader: SCM Micro / SCL3711-NFC&RW opened
# using a DEsfire EV1:
> 4a0100
Tx: 4a  01  00  
Rx: 01  01  03  44  20  07  04  1e  20  61  80  1d  80  06  75  77  81  02  80  
# Removing the tag
> 0006
Tx: 00  06  
Rx: RF Transmission Error
> Bye!

$ pn53x-tamashell 
# works as normal
NFC reader: SCM Micro / SCL3711-NFC&RW opened
# Using a JCOP31 2.4.1
> 4a0100
Tx: 4a  01  00  
Rx: 01  01  00  48  20  07  04  13  14  21  8b  20  80  0d  78  77  b1  02  4a  
43  4f  50  76  32  34  31  
# Removing the tag
> 0006
Tx: 00  06  
Rx: RF Transmission Error
# At this point communication with PN533 is still possible
> Bye!

$ pn53x-tamashell 
error   libnfc.driver.pn53x_usb Unable to set USB configuration (Connection timed 
out)
pn53x-tamashell: ERROR: Unable to open NFC device.

Solution can be to implement ourselves a ping as we did for -4B on PN532

Original issue reported on code.google.com by yob...@gmail.com on 31 Jan 2014 at 9:14

marcus905 / libnfc

nfc_initiator_target_is_present() makes PN533 unusable after some -4A cards #267