library/ipaserver_test: Revert to IPA upstream code for pkcs12 files

The function load_pkcs12 should not be skipped to verify the given
certificates. After the certificates have been verified and the temporary
certificate copies have been generated, these files are copied to
/etc/ipa/.tmp_pkcs12_* as the temporary files will simply be removed as
soon as the file descriptors have been closed.

Additionally the [http,dirsrv,pkinit]_pkcs12_info is recreated to point to
the copied temporary files.

With this revertion the need to change other modules has been rediced to
the minium, the IPA upstream code can simply be used.

The passed back certificates [http,dirsrv,pkinit]_ca_cert are encoded using
encode_certificate.