add encryption plugins to deb packages

debian/dist/Debian/mariadb-server-10.1.files.in

 usr/lib/mysql/plugin/auth_pam.so
 usr/lib/mysql/plugin/auth_socket.so
+usr/lib/mysql/plugin/file_key_management.so
 usr/lib/mysql/plugin/ha_archive.so
 usr/lib/mysql/plugin/ha_blackhole.so
 usr/lib/mysql/plugin/ha_federated.so

debian/dist/Ubuntu/mariadb-server-10.1.files.in

 usr/lib/mysql/plugin/auth_pam.so
 usr/lib/mysql/plugin/auth_socket.so
+usr/lib/mysql/plugin/file_key_management.so
 usr/lib/mysql/plugin/ha_archive.so
 usr/lib/mysql/plugin/ha_blackhole.so
 usr/lib/mysql/plugin/ha_federated.so

debian/mariadb-test-10.1.files

+usr/lib/mysql/plugin/debug_key_management.so
+usr/lib/mysql/plugin/example_key_management.so
 usr/lib/mysql/plugin/dialog_examples.so
 usr/lib/mysql/plugin/auth_test_plugin.so
 usr/lib/mysql/plugin/qa_auth_interface.so