BUG-874 Remove rolback cabaility advertised by config netconf

The rollback on error option is not supported by the netconf server endpoint for config subsystem therefore it cannot advertise rollback on error capability.
If it is present in message, the rpc will fail.

Change-Id: If32113aa77d9ef5d614b143741d1d04fbdc0d22d
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>
BUG-874 Add none default operation to delete requests (netconf-connector)

Delete requests now contain <default-operation>none</default-operation> tag to prevent modification of the data tree on remote device when deleting nested nodes.

Change-Id: Id5cb7945b6845d6ccea7ef71a07d914cdf5f2ed9
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>