Issue Description

log_crashes in tests/instances.tcl — the multi-instance harness used by both make test-sentinel and make test-cluster — scans every instance's err.txt with find_valgrind_errors unconditionally:

set logs [glob */err.txt]
foreach log $logs {
    set res [find_valgrind_errors $log true]
    if {$res != ""} {
        puts $res
        incr ::failed
    }
}

The main test framework runs the identical scan only behind a valgrind guard — in tests/support/server.tcl, check_valgrind_errors is called from kill_server inside if {$::valgrind}.

find_valgrind_errors' fallback (in tests/support/util.tcl) treats any stderr that lacks a valgrind leak-free summary as an error:

# Look for the absence of a leak free summary
# (happens when the server isn't terminated properly).
if {(![regexp -- {definitely lost: 0 bytes} $buf] &&
     ![regexp -- {no leaks are possible} $buf])} {
    return $buf
}

When the suite is not running under valgrind, that summary is never present, so any non-empty err.txt is flagged as a failure.

Concrete trigger

On hosts whose CPU does not expose the constant_tsc flag (common inside VMs / LXD), every valkey-server and valkey-sentinel prints to stderr at startup (src/monotonic.c):

monotonic: x86 linux, 'constant_tsc' flag not present

The sentinel suite then reports exactly 10 failures (5 sentinel + 5 valkey instances) on every run — even though every individual test passes and no assertion fails. The cluster suite shares this harness and is affected identically. On hosts that expose constant_tsc the message is never printed, so the bug is invisible — which is why it only surfaces in certain CI/VM environments.

Fix

Wrap the valgrind err.txt scan in if {$::valgrind}, mirroring server.tcl. The sanitizer scan immediately below is left unguarded, matching check_sanitizer_errors, which always runs. No test coverage is lost.

if {$::valgrind} {
    set logs [glob */err.txt]
    foreach log $logs {
        set res [find_valgrind_errors $log true]
        if {$res != ""} {
            puts $res
            incr ::failed
        }
    }
}