import: allow importing configurations with inline certificates (rh #1157817)

Configuration files for openvpn can contain inline files (certificates).
http://sourceforge.net/p/openvpn/openvpn/ci/0979ec7e9109da95ad56e9365a89701fee11c72c
http://sourceforge.net/p/openvpn/openvpn/ci/d40f2b204b78ace5c2c9c3007887571ca5a2ec11

Let's support inline certificates while importing openvpn configuration.

Example config:
https://www.frootvpn.com/files/frootvpn.ovpn

https://bugzilla.redhat.com/show_bug.cgi?id=1157817