lang: Use universal way to retrieve load

Sysinfo is not supported on macOS and results in a build error.

test/shell/load0.sh

@@ -0,0 +1,48 @@
+#!/bin/bash -e
+
+if env | grep -q -e '^TRAVIS=true$' && [[ $(uname) == "Darwin" ]]; then
+	# loadavg glibc calls don't seem to work properly on osx OS in travis
+	echo "Travis and Jenkins give wonky results here, skipping test!"
+	exit
+fi
+
+set -o errexit
+set -o pipefail
+
+# Expected load average values eg: load average: 1.64306640625, 1.8076171875, 1.82958984375
+# High precision results are preferred (more than the 2 digits in /proc/loadavg at least).
+# Precision varies (eg: 4, 9 or 11 digits). Hence no strict check for precision but
+# anything above 3 will do. It is assumed we will hardly ever get a precision lower than 3 digits
+# from the current implementations. Otherwise this test would need to be revised.
+regex="load average: [0-9]\,[0-9]{3,}, [0-9]\,[0-9]{3,}, [0-9]\,[0-9]{3,}"
+
+tmpdir="$($mktemp --tmpdir -d tmp.XXX)"
+
+# macOS workaround https://github.com/purpleidea/mgmt/issues/33
+touch "$tmpdir/loadavg"
+
+cat > "$tmpdir/load0.mcl" <<EOF
+\$theload = load()
+
+\$x1 = structlookup(\$theload, "x1")
+\$x5 = structlookup(\$theload, "x5")
+\$x15 = structlookup(\$theload, "x15")
+
+file "${tmpdir}/loadavg" {
+	content => printf("load average: %f, %f, %f", \$x1, \$x5, \$x15),
+	state => "exists",
+}
+EOF
+
+$timeout --kill-after=30s 15s ./mgmt run --tmp-prefix --converged-timeout=1 --lang "$tmpdir/load0.mcl"  &
+pid=$!
+wait $pid	# get exit status
+e=$?
+
+set +e
+egrep "$regex" "$tmpdir/loadavg" || fail_test "Could not match $tmpdir/loadavg to '$regex'."
+
+# cleanup if everything went well
+rm -r "$tmpdir"
+
+exit $e