tests: rename suite 'wal' to 'wal_off'.

test/box/admin.result

test/box/admin.test.lua

test/box/reconfigure.result

test/box/reconfigure.test.lua

test/wal_off/alter.result

test/wal_off/alter.test.lua

test/wal_off/func_max.result

test/wal_off/func_max.test.lua

test/wal_off/lua.result

test/wal_off/lua.test.lua

test/wal_off/oom.result

test/wal_off/oom.test.lua

test/wal_off/rtree_benchmark.result

test/wal_off/rtree_benchmark.test.lua

test/wal_off/suite.ini

test/wal_off/tuple.result

test/wal_off/tuple.test.lua

test/wal_off/wal.lua

test/wal_off/wal_mode.result

test/wal_off/wal_mode.test.lua