USyncClient: close when destructor is called.
USyncClient: close when destructor is called.

Fixes a race condition, the Socket was allready closed at the UClient level,
but callbacks using locks from USyncClient could be called.

	* src/liburbi/usyncclient.cc (~USyncClient): Call close() and
	libport's waitForDestructionPermission() mechanism.

aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi