Unit tests for hv_xen._GetCommand
Unit tests for hv_xen._GetCommand

This patch adds unit tests for the current state of the
'GetCommand' method. The tests are rather trivial, but
having tests before starting to refactor seems to be
a good idea.

Signed-off-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>
Reviewed-by: Thomas Thrainer <98bdeac947eb8ca18146e9ce7f092788ec242cd1@google.com>

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