valgrind: silence worrying invalid pthread lock/unlock warnings on exit

Invalid read of size 4
   at 0x57F48E0: __pthread_mutex_unlock_full (in /usr/lib64/libpthread-2.21.so)
   by 0x4E903F7: osl_releaseMutex (mutex.cxx:136)
   by 0xB3EECF0: osl::Mutex::release() (mutex.hxx:74)
   by 0xB3EF92C: osl::Guard<osl::Mutex>::~Guard() (mutex.hxx:135)
   by 0xB3F755A: SvtCommandOptions::~SvtCommandOptions() (cmdoptions.cxx:318)
   by 0xB3F75B3: SvtCommandOptions::~SvtCommandOptions() (cmdoptions.cxx:328)
   by 0x2B13BDE9: std::default_delete<SvtCommandOptions>::operator()(SvtCommandOptions*) const (unique_ptr.h:76)
   by 0x2B13A3C6: std::unique_ptr<SvtCommandOptions, std::default_delete<SvtCommandOptions> >::~unique_ptr() (unique_ptr.h:236)
   by 0x2B134063: framework::Desktop::~Desktop() (desktop.cxx:183)
   by 0x2B13418B: framework::Desktop::~Desktop() (desktop.cxx:187)
   by 0x79892AD: cppu::OWeakObject::release() (weak.cxx:205)
   by 0x2B1399B7: framework::Desktop::release() (desktop.hxx:133)
   by 0x2B13B860: rtl::Reference<framework::Desktop>::~Reference() (ref.hxx:81)
   by 0x2B13956B: (anonymous namespace)::Instance::~Instance() (desktop.cxx:1780)
   by 0x54635D7: __run_exit_handlers (in /usr/lib64/libc-2.21.so)
   by 0x5463624: exit (in /usr/lib64/libc-2.21.so)

Change-Id: I98e0e70567ab39a06813fd9b614ba1e04ec22bd1

framework/source/services/desktop.cxx

@@ -1073,6 +1073,7 @@ void SAL_CALL Desktop::disposing()
     m_xQuickLauncher.clear();
     m_xSWThreadManager.clear();
     m_xSfxTerminator.clear();
+    m_xCommandOptions.reset();
 
     // From this point nothing will work further on this object ...
     // excepting our dtor() .-)