[4489] Addressed review comments.

The only review item not addressed with this commit is the
implementation of unit test that operates on the read only
database, i.e. the database containing tables on which the
given user only has SELECT privileges.

src/share/database/scripts/mysql/dhcpdb_create.mysql

@@ -465,6 +465,11 @@ ALTER TABLE dhcp6_options
     ADD CONSTRAINT fk_dhcp6_option_scope FOREIGN KEY (scope_id)
     REFERENCES dhcp_option_scope (scope_id);
 
+# Add UNSIGNED to reservation_id
+ALTER TABLE ipv6_reservations
+    MODIFY reservation_id INT UNSIGNED NOT NULL AUTO_INCREMENT;
+
+
 # Update the schema version number
 UPDATE schema_version
 SET version = '4', minor = '2';