core: Modify constructor to be compatible with caller method

CreateOvfStoresForStorageDomainCommand is being called without context
although its constructor is only supported with context parameter,
so we will always get runtime exception when the command is being called.

The proposed fix remove the context from the
CreateOvfStoresForStorageDomainCommand constructor

Change-Id: Ib2cd44301ccf992541ecd0f9572fd7afde4a123d
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>