Remove namespace from variable name elements in Events "propertyset" to comply with UDAv1.1

See UPNP Device Architecture v1.1, section 4.3.2 :
<variableName>
REQUIRED. Element is name of a state variable that changed (<name> sub element of
<stateVariable> element in service description). MUST NOT be qualified with any namespace. Value
is the new value for this state variable. Case sensitive. Single data type as specified by UPnP service
description.