UI: Capabilities for ginger

Show and hide different component based on different hosts.

Signed-off-by: Wen Wang <wenwang@linux.vnet.ibm.com>
models/interfaces.py: fixing an 'is not defined' error

The method was being called as '_get_all_libvirt_interfaces' instead
of 'self._get_all_libvirt_interfaces'.

Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
models/ibm_sep.py: adding 'is_feature_available()' method

Adding the is_feature_available method so the SEP feature can be
flagged as 'False' by the Capabilities API if there are no SEP
support in the host.

Signed-off-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>