Clear the error state in every synchronous manager call
Clear the error state in every synchronous manager call

Prevents synchronous calls from possibly reporting the error which may
have occurred in a previous call if the engine does not explicitly
set it to QContactManager::NoError, as this is done by us explicitly.

Relates to task QTMOBILITY-167.

tmcguire/qt-mobility,KDE/android-qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,tmcguire/qt-mobility,tmcguire/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,tmcguire/qt-mobility,KDE/android-qt-mobility,KDE/android-qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,enthought/qt-mobility,KDE/android-qt-mobility,enthought/qt-mobility