library probes: don't add libraries to visited_modules

library probes: don't add libraries to visited_modules

The dwarf_query's visited_modules set is used to keep track of which
modules are visited for suggestions. It works by emptying out the visited
modules into the dwarf_builder's modules_seen after we're done iterating
through the modules. By the end, modules_seen contains the full list of
modules to suggest from.

Since .library(glob) probes resolve to multiple probes for each matching
library, dwarf_builder's modules_seen will already pick each of them up
from the individually created dwarf_query objects.

So in the end, the modules_seen from which we make suggestions will
already contain them.