coroparse: Be more strict in what is parsed

coroparse: Be more strict in what is parsed

Corosync parser is not very clever, but it is able to detect more errors
without too much code.

1. Check if section name is not empty (just '{' character)
2. Check if there is no extra characters after opening bracket '{'
3. Check if there is no extra characters after or before closing bracket
   '}'
4. Check if line is opening section, closing section or key/value

So following examples are reported as error:

totem {
    version: 2
}}}}}}}}}}

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>