Fix unitialized field in HWC2on1Adapter

Layer acquire fence file descriptor was not always initialized. In
the case of a SolidColor layer, the file descriptor was left set to
value 0 (stdin) which after call to set would be closed by the
adapter leading to system unstability.

Test: Angler eng devices and AUPT

Change-Id: Ic931d8cf9b0c6ca8d56c7a0ed7a7f586bf072505