Fixed test for Lua 5.1
Fixed test for Lua 5.1

In Lua 5.1 string.format %s pattern did not apply tostring
to correspoding argument.

mpeterv/luacheck,tst2005/luacheck,kidaa/luacheck,linuxmaniac/luacheck,tst2005/luacheck,mpeterv/luacheck,xpol/luacheck,mpeterv/luacheck,xpol/luacheck,adan830/luacheck,linuxmaniac/luacheck,kidaa/luacheck,xpol/luacheck,adan830/luacheck