Previous attempts to constrain execution of `resize` to only TTYs did
not properly handle situations when `tty` would return the string "not a
tty". The symptom is "/etc/profile: line 34: test: too many arguments".
Fix this by utilizing the exit code of `tty`. Also use `case` instead of
`cut` to eliminate a subshell.
Signed-off-by: Richard Tollerton <rich.tollerton@ni.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
