Conflict definition in SLAPI_ATTR_FLAG macros

Bug description:
It turned out these 2 macros had conflict values.
  SLAPI_ATTR_FLAG_NORMALIZED_CIS 0x0400 /* the attr value is normalized ..
  SLAPI_ATTR_FLAG_NOEXPOSE       0x0400 /* the attr value is not exposed */
SLAPI_ATTR_FLAG_NORMALIZED_CIS was introduced with the commit
c0151f78509c35250095da6e2785842337963008.

Fix description: Define SLAPI_ATTR_FLAG_NOEXPOSE with 0x0800
which is not used by any other SLAPI_ATTR_FLAG macros.

ldap/servers/slapd/slapi-plugin.h

@@ -193,7 +193,7 @@ NSPR_API(PRUint32) PR_fprintf(struct PRFileDesc* fd, const char *fmt, ...)
  * \see slapi_value_set_flags()
  * \see slapi_values_set_flags()
  */
-#define SLAPI_ATTR_FLAG_NOEXPOSE	0x0400	/* the attr value is not exposed */
+#define SLAPI_ATTR_FLAG_NOEXPOSE	0x0800	/* the attr value is not exposed */
 
 /* operation flags */
 #define SLAPI_OP_FLAG_INTERNAL		0x00020 /* An operation generated by the core server or a plugin. */