require fails in lua script invoked by tt run

Create two simple scripts:

• router.lua:

#!/usr/bin/env tarantool

-- Call a configuration provider
cfg = require('localcfg')
print(cfg)
os.exit(0)

• localcfg.lua in the same directory:
  return {}

From any other directory try to run router with tarantool:

$ tarantool instances.enabled/crud_app/router.lua 
table: 0x400134e0

and tt run:

$ tt run instances.enabled/crud_app/router.lua 
Failed to run instance: instances.enabled/crud_app/router.lua, error: "instances.enabled/crud_app/router.lua:4: module 'localcfg' not found:
	no field package.preload['localcfg']

localcfg.lua cannot be found.

After fixing this issue, please check that tt start also works with router application script.

Reproduce the behavior with the router.lua and localcfg.lua scripts described in the issue, comparing tarantool with tt run. Start at the tt run and tt start entry points and trace how the application script is launched. Done means localcfg.lua is found when invoked from another directory and both tt run and tt start work with the router application script.