netifd: Fix proto shell setup/teardwon race condition

Fix setup race condition when proto shell is in teardown or setup_abort state when setup cmd is received.
Don't change the proto shell state and launch no setup in these conditions so the proto shell teardown
timeout handler does not kill the wrong processes and proto_shell_task_finish takes action on the correct
teardown state.
Don't launch a new setup action when already in setup state.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>