cave resolve world -c doesn't handle correctly suggestions

[keruspe]

Package a suggests installing package b. Package c depends on package b. Suggestions are blacklisted in suggestions.conf (*/* -*/*).

Installation package a. Installation package c (and thus b with it). Uninstallation package c.

Package b remains installed and never get caught by resolve world -c since suggestions are blacklisted.

We should check if they are installed before rejecting them from the world resolution.

[keruspe]

Typso discovered while investigating

[keruspe]

Fix the world resolution

[ciaranm]

Ta