Fix cylc-search for directories without suite.rc

[kinow]

cylc search /home/kinow/cylc-run/five/share foo*

Works fine. But using another directory, the previous version would print usage and exit with a non zero exit code. Current version in master is broken.

$ cylc search /home/kinow/cylc-run/five/share foo*
Traceback (most recent call last):
  File "/home/kinow/Development/python/workspace/cylc/venv/bin/cylc-search", line 7, in <module>
    exec(compile(f.read(), __file__, 'exec'))
  File "/home/kinow/Development/python/workspace/cylc/bin/cylc-search", line 196, in <module>
    main()
  File "/home/kinow/Development/python/workspace/cylc/lib/cylc/terminal.py", line 65, in wrapper
    function(*args, **kwargs)
  File "/home/kinow/Development/python/workspace/cylc/bin/cylc-search", line 94, in main
    parser.error("File not found: " + suiterc)
NameError: name 'parser' is not defined

This small fix unfortunately removes the function to parse args (which is good to encapsulate that part...) in order to keep the exact previous behaviour without having to copy or mimic the calls to print usage and exit status.

[kinow]

Note: these small issues are left-over of Cylc7 -> Cylc8 migration (packaging, refactorings, py3, etc), so I am not creating tickets and worrying about the changelog, as I think these issues are not interesting for users concerned about updating to Cylc 8 👍