02-test_errstr.t: make robust on `openssl errstr` crashes #1229

Job	Run time
run-checker (no-cmp)	4m 43s
run-checker (no-cms)	5m 3s
run-checker (no-dgram)	4m 45s
run-checker (no-dh)	4m 58s
run-checker (no-dtls)	5m 2s
run-checker (no-ec)	4m 18s
run-checker (no-ecx)	4m 47s
run-checker (no-http)	4m 58s
run-checker (no-legacy)	4m 59s
run-checker (no-sock)	4m 33s
run-checker (enable-ssl-trace)	5m 5s
run-checker (no-stdio)	2m 13s
run-checker (no-threads)	4m 59s
run-checker (no-thread-pool)	5m 20s
run-checker (no-default-thread-pool)	5m 8s
run-checker (no-tls)	4m 36s
run-checker (no-tls1_2)	4m 54s
run-checker (no-tls1_3)	4m 42s
run-checker (enable-trace enable-fips)	5m 33s
run-checker (no-ui)	5m 7s
run-checker (no-quic)	4m 42s
	1h 40m 25s

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