Make the keystore domain enforcing.

Change-Id: I8f4964fb31e91d9f384ef05df5acdcdd45dec08b
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

keystore.te

 type keystore, domain;
-permissive keystore;
 type keystore_exec, exec_type, file_type;
 
 # keystore daemon