hv_xen: Prepare for unit tests, remove {static,class}method
hv_xen: Prepare for unit tests, remove {static,class}method

Unit tests will have to specify a custom Xen configuration directory (a
temporary directory). To this end “hv_xen.XenHypervisor” and its two
derived classes are modified to have fewer static and class methods. A
new private attribute for the configuration directory is also added (to
be used in test code).

Signed-off-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>
Reviewed-by: Bernardo Dal Seno <dcdd79c5479cb9d1329ec01d126f02cb045aa103@google.com>

bitemyapp/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,dimara/ganeti,yiannist/ganeti,leshchevds/ganeti,apyrgio/snf-ganeti,grnet/snf-ganeti,andir/ganeti,ganeti/ganeti,apyrgio/ganeti,apyrgio/ganeti,yiannist/ganeti,dimara/ganeti,onponomarev/ganeti,ganeti/ganeti,bitemyapp/ganeti,andir/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,leshchevds/ganeti,grnet/snf-ganeti,mbakke/ganeti,andir/ganeti,mbakke/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,onponomarev/ganeti,leshchevds/ganeti