SFTP VFS provider: write access when id_rsa file generated with a passphrase

1. Create new user account on host1;
2. Create a .ssh directory in user home folder, permission 700;
3. Create private and public key pair by ssh-keygen using passphrase;
4. Copy the user public key into authorized_keys;
5. Copy the private key to host2;
6. Open attached transformtaion on host2;
7. Edit Kettle.Properties file and add
vfs.sftp.AuthKeyPassphrase.<host1>=<passphrase>
vfs.sftp.identity.<host1>=<path to the private key file>
8. Run transformation. In Run Options set appropriate value for the sftp_authkey_host and sftp_authkey_username parameters.
9. Check log.

Log contains error message:

Text file output.0 - ERROR (version 7.0-QAT-239, build 1 from 2016-07-26 22.14.09 by buildguy) : org.pentaho.di.core.exception.KettleException:
Text file output.0 - Error opening new file : org.pentaho.di.core.exception.KettleFileException:
Text file output.0 - Unable to get VFS File object for filename 'sftp://user1@10.6.117.149/home/user1/file_out.txt' : Could not connect to SFTP server at "sftp://user1@10.6.117.149/".

Try to run transformation and use a id_rsa file that has not an associated passphrase, the transformation can perform the "Text file output" step without ERROR above.