replace dlclose() with CloseNativeLibrary() in vulkan layer

With its 2nd argument, the CloseNativeLibrary() can close
a library opened by either dlopen() or OpenNativeLibrary().
Thus, this change covers the native case missed when the
dlclose() was directly called.

Test: [CTS] run cts -m CtsGpuToolsHostTestCases -a armeabi-v7a

Change-Id: Id81e8042292cd95f0be18abdd53e3e62ed448f8e
Signed-off-by: Jacky.Deng <jacky.deng@intel.com>
Signed-off-by: Jianxun Zhang <jianxun.zhang@intel.com>