Fix memory-safety and correctness bugs surfaced by Coverity audit (part 5) - #22279

…rt 5) (#22279)

* dictionary: retry view inserts after stale entry cleanup

Coverity CID 414657 (REVERSE_INULL): a rejected item-acquire path in
`dict_item_add_or_reset_value_and_acquire()` left `item` non-NULL, so the
`do/while` loop exited instead of retrying after stale view-entry cleanup.
Clear `item` before retrying and cover the stale-view replacement path in the
existing dictionary unittest.

* dictionary: release view item on stale replacement branch in unittest

Release the acquired `view_item2` on the stale/deleted failure branch of
the view-replacement regression test, matching the release on the success
branch so the test does not leak an acquired reference.

* ebpf.plugin: make module state accesses atomic

Coverity CID 405093 (MISSING_LOCK): ebpf_module.enabled was sampled from
stats and shutdown paths while module exit code updated the same plain enum
under a different synchronization regime. Convert the live cross-thread
reads and writes to atomic helpers so those state checks stay defined
without changing the existing lock layout.

* ebpf: start function threads outside cleanup lock

Coverity CID 405089 (SLEEP): Function-triggered eBPF socket restarts held ebpf_exit_cleanup while nd_thread_create could wait and retry. Gate the new thread until state is published, so creation happens outside the cleanup mutex without racing shutdown.

* systemd-journal: pass depth+1 to recursive directory scan

nd_journal_directory_scan_recursively() used depth++ (post-increment)
when recursing into subdirectories, which passes the caller's current
depth to the recursive call and then increments the caller's local
counter across sibling iterations. Effect: the 2nd, 3rd, ... sibling
subdirectories of the same parent get inflated depths and prematurely
hit VAR_LOG_JOURNAL_MAX_DEPTH, silently truncating legitimate scans.

Use depth + 1 instead so every recursion starts exactly one level
deeper than the current frame.

* systemd-journal: log visited directory tracking failures

When dictionary_set() returns NULL the recursive scan still closes the
current directory and bails out, but an operator looking at truncated
journal discovery had no way to know why. Log the failure before
returning so the condition is diagnosable.

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Co-authored-by: Costa Tsaousis <costa@netdata.cloud>
(cherry picked from commit 42097e1)