Update license of lsm/selinux.c

Change the license from GPL to LGPL to avoid a tricky license situation
for liblxc.so.

Signed-off-by: Jonas Eriksson <jonas.eriksson@enea.com>
Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>