usbredir: fix leaks introduced by lz4 patch
usbredir: fix leaks introduced by lz4 patch

While reviewing lz4 patch, I found that there are potential leaks. This
is untested, fyi. It would be nice if someone could confirm with running
ASAN for example.

Signed-off-by: Marc-André Lureau <a6f2b960a4aca61381fc650a67901b2ac8e83e6d@redhat.com>
Reviewed-by: Snir Sheriber <a22152bc672d3e177f23883338efc60c231ec881@redhat.com>

flexVDI/spice-gtk,fgouget/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk