plugins/router_cache: fix memory leak in uwsgi_router_cache_store

Reported by Coverity as CID #995792.
plugins/carbon: fix memory leak in carbon_post_init

Reported by Coverity as CID #995791
core/emperor: fix memory leak in uwsgi_emperor_vassal_start

Reported by Coverity as CID #995786.
Merge pull request #208 from xrmx/coverity11

More issues reported by Coverity