Previously, the possible extra certificate(s) from a PKCS#12 file was
added once for each authentication attempt. This resulted in OpenSSL
concatenating the certificates multiple time (add one copy for each try
during the wpa_supplicant process lifetime). Fix this by clearing the
extra chain certificates before adding new ones when using OpenSSL 1.0.1
or newer that include the needed function.
Signed-off-by: Jouni Malinen <j@w1.fi>