reading keystore.p12 sometimes read not keyEntry as a first alias

[marek-veber]

the code:

final Enumeration<String> aliases = getAliases(keystore);

returns aliases of two types:

keystore.isKeyEntry(a) == true

and

keystore.isCertificateEntry(a) == true

But using method select first one can be randomly unvanted CertificateEntry (not required KeyEntry) ;)

So, sometimes initialisation fails with an error such as "bad key format", while using certificate as a key ;(

[todvora]

Merged, thank you for your contribution!