SMI-S Plugin: Remove unused methods from SmisCommon
SMI-S Plugin: Remove unused methods from SmisCommon

 * Removed these methods and properties as they are not used out side of
   SmisCommon:
    InvokeMethod()
    last_request
    last_reply

 * For SmisCommon internal use of these methods and properties, changed them
   to use self._wbem_conn instead.

Signed-off-by: Gris Ge <e24f3acbe39bf94f92e8af3c48f8852106ad5ad7@redhat.com>

joehandzik/libstoragemgmt,cathay4t/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,jumitche/libstoragemgmt,lazy404/libstoragemgmt,tasleson/libstoragemgmt,tasleson/libstoragemgmt,libstorage/libstoragemgmt,tasleson/libstoragemgmt,libstorage/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,lazy404/libstoragemgmt,libstorage/libstoragemgmt,cathay4t/libstoragemgmt,joehandzik/libstoragemgmt,cathay4t/libstoragemgmt,jumitche/libstoragemgmt,jumitche/libstoragemgmt,jumitche/libstoragemgmt,cathay4t/libstoragemgmt,joehandzik/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,joehandzik/libstoragemgmt,jumitche/libstoragemgmt,tasleson/libstoragemgmt,HP-Scale-out-Storage/libstoragemgmt,cathay4t/libstoragemgmt,libstorage/libstoragemgmt,libstorage/libstoragemgmt,lazy404/libstoragemgmt,tasleson/libstoragemgmt,lazy404/libstoragemgmt