python: replace aliases with corresponding type names

Aliases are not used in the selinux database. When user enters a type
alias as a parameter it should be converted to the corresponding type
in order to be processed correctly further in the userspace logic.

Fixes e.g.:

\#sepolicy transition -s phpfpm_t
/* where phpfpm_t is a type alias of httpd_t */

Traceback (most recent call last):
  File "/usr/bin/sepolicy", line 691, in <module>
    args.func(args)
  File "/usr/bin/sepolicy", line 458, in transition
    mytrans = setrans(args.source, args.target)
  File "/usr/lib/python3.6/site-packages/sepolicy/transition.py", line 48, in __init__
    self._process(self.source)
  File "/usr/lib/python3.6/site-packages/sepolicy/transition.py", line 54, in _process
    trans = _get_trans(source)
  File "/usr/lib/python3.6/site-packages/sepolicy/transition.py", line 36, in _get_trans
    src_list = [src] + list(filter(lambda x: x['name'] == src, sepolicy.get_all_types_info()))[0]['attributes']
IndexError: list index out of range
3 files changed