surfaceflinger: handle executeCommands transaction errors

Unlike other functions, executeCommands both sends and receives
handles.  It can fail for reasons such as out-of-fd.  We want to
protect SurfaceFlinger against out-of-fd.

Bug: 65449888
Test: manual
Change-Id: Id9420dbd6d0a943737c90bd3a1ae0df3805a4cb0