content size checks are not valid for LOCK

fixes 

````
00:09:55.905 There were 2 failures:
00:09:55.905 
00:09:55.905 1) Test_OC_Connector_Sabre_File::testSimplePutFailsOnRename
00:09:55.905 Failed asserting that exception of type "PHPUnit_Framework_Error_Notice" matches expected exception "\Sabre\DAV\Exception". Message was: "Undefined index: REQUEST_METHOD".
00:09:55.905 
00:09:55.905 
00:09:55.905 2) Test_OC_Connector_Sabre_File::testUploadAbort
00:09:55.908 Failed asserting that exception of type "PHPUnit_Framework_Error_Notice" matches expected exception "\Sabre\DAV\Exception\BadRequest". Message was: "Undefined index: REQUEST_METHOD".
00:09:55.908