circleci: Set $TERM to fix tput & curses errors
circleci: Set $TERM to fix tput & curses errors

This should fix
`test_stbt_control_as_stbt_record_control_recorder__default_keymap`
which needs curses.

It should also silence warnings from `tput` which is used by
`run-tests.sh` to output pretty colours.

stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester