MEDIUM: fcgi-app: properly postresolve logsrvs

MEDIUM: fcgi-app: properly postresolve logsrvs

Now that we have postresolve_logsrv_list() function, we make use of it
for fcgi-app log postparsing logic.

This will allow this kind of config to work:
  |fcgi-app test
  |        docroot /
  |        log-stderr tcp@127.0.0.1:514 local0

Plus, consistency checks will also be performed as for regular log
directives used from global, log-forward or proxy sections.