Fix uninitialized go connection info

[grcevski]

We had checks in the eBPF code for finding the connection information, but we didn't check if we actually found the final connection pointer, or the file descriptor. In this scenario we'd generate bogus ip information which might cause large number of DNS queries.

I also made sure empty IP addresses end up as empty strings, so the name resolver will ignore them.

Fixes #895

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 73.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 73.02%. Comparing base (635938c) to head (caeb95b).

Files	Patch %	Lines
pkg/internal/ebpf/common/common.go	66.66%	2 Missing and 2 partials ⚠️

❗ There is a different number of reports uploaded between BASE (635938c) and HEAD (caeb95b). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (635938c)	HEAD (caeb95b)
unittests	1	0

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1019      +/-   ##
==========================================
- Coverage   81.60%   73.02%   -8.59%     
==========================================
  Files         137      136       -1     
  Lines       10935    10914      -21     
==========================================
- Hits         8924     7970     -954     
- Misses       1502     2307     +805     
- Partials      509      637     +128     

Flag	Coverage Δ
integration-test	56.56% <73.33%> (+0.17%)	⬆️
k8s-integration-test	59.02% <66.66%> (+0.02%)	⬆️
oats-test	37.33% <66.66%> (-0.06%)	⬇️
unittests	?

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[mariomac]

LGTM! Before merging, I'd recommend merging the main branch and regenerating the BPF binaries.