Reworked password handling for import/export

Reworked password handling for import/export

- Always use callback.
- Return INVALID_PASSWORD for combinations that do support password,
  it was not required for import but was given in params.
- Return INVALID_PARAM for combinations that do not support password
  while it was given in params. For both, import and export.
- PKCS8 always requires a password.
- Added few special cases to differentiate INV_PARAM and INV_PASSWORD.

Change-Id: I171e89125600151e33178eadc3df6b6004987f3c