Add missing freeHandle to setTo

On inspection, it looks like without this added call, the possibility
exists to leak a handle if a populated handle is "set".

Test:  local build
Change-Id: I9a262fbc1af72ae498dd0e2172216414a263c7fd
diff --git a/base/HidlSupport.cpp b/base/HidlSupport.cpp
index 912a5b0..7320f3f 100644
--- a/base/HidlSupport.cpp
+++ b/base/HidlSupport.cpp
@@ -156,6 +156,7 @@
 }
 
 void hidl_handle::setTo(native_handle_t* handle, bool shouldOwn) {
+    freeHandle();
     mHandle = handle;
     mOwnsHandle = shouldOwn;
 }