Don't setup openssl if the openssl binary cannot be found

[s0undt3ch]

  Traceback (most recent call last):
    File "/opt/saltstack/salt/lib/python3.10/site.py", line 186, in addpackage
      exec(line)
    File "<string>", line 1, in <module>
    File "/opt/saltstack/salt/lib/python3.10/site-packages/relenv/runtime.py", line 969, in bootstrap
      setup_openssl()
    File "/opt/saltstack/salt/lib/python3.10/site-packages/relenv/runtime.py", line 802, in setup_openssl
      proc = subprocess.run(
    File "/opt/saltstack/salt/lib/python3.10/subprocess.py", line 503, in run
      with Popen(*popenargs, **kwargs) as process:
    File "/opt/saltstack/salt/lib/python3.10/subprocess.py", line 971, in __init__
      self._execute_child(args, executable, preexec_fn, close_fds,
    File "/opt/saltstack/salt/lib/python3.10/subprocess.py", line 1738, in _execute_child
      and os.path.dirname(executable)
    File "/opt/saltstack/salt/lib/python3.10/posixpath.py", line 152, in dirname
      p = os.fspath(p)
  TypeError: expected str, bytes or os.PathLike object, not NoneType