openssl: Support unencrypted PKCS#8 private keys
openssl: Support unencrypted PKCS#8 private keys

This is verified working with the output from
"openssl pkcs12 -in foo.p12 -nodes" (v1.0.1).

Signed-off-by: Kevin Cernekee <3105dbb3dd63fbb4f6371cfb04adc6726f76c56b@gmail.com>

don-johnny/openconnect,nmav/openconnect-mine,chadcatlett/openconnect,lins05/openconnect,atyndall/openconnect,brandt/openconnect,liiir1985/openconnect,neshema/openconnect,matlockx/openconnect,don-johnny/openconnect,matlockx/openconnect,chadcatlett/openconnect,nmav/openconnect-mine,cernekee/openconnect,cernekee/openconnect,lins05/openconnect,don-johnny/openconnect,matlockx/openconnect,mveplus/openconnect-client,mtmiller/openconnect,mveplus/openconnect-client,liiir1985/openconnect,cernekee/openconnect,lins05/openconnect,nmav/openconnect-mine,atyndall/openconnect,mtmiller/openconnect,mtmiller/openconnect,atyndall/openconnect,neshema/openconnect,cernekee/openconnect,atyndall/openconnect,brandt/openconnect,chadcatlett/openconnect,matlockx/openconnect,chadcatlett/openconnect,neshema/openconnect,nmav/openconnect-mine,liiir1985/openconnect,mveplus/openconnect-client,don-johnny/openconnect,mveplus/openconnect-client,brandt/openconnect,mtmiller/openconnect,brandt/openconnect,neshema/openconnect,liiir1985/openconnect,lins05/openconnect