loader: Fix several leaks
loader: Fix several leaks

Fix several leaks caught by Valgrind.  This change should fix all
memory leaks caught by David Hubbard in pull-request #811.

Change-Id: I55d7f3a6abbc32fde182702c4b9cf1041107c6df

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools