fix pressure metric collection fails on systems that do not expose a …

…full CPU stat prometheus#3051 (prometheus#3054)

Signed-off-by: joey <zchengjoey@gmail.com>
Signed-off-by: Vitaly Zhuravlev <v-zhuravlev@users.noreply.github.com>

collector/pressure_linux.go

@@ -106,7 +106,7 @@ func (c *pressureStatsCollector) Update(ch chan<- prometheus.Metric) error {
 			level.Debug(c.logger).Log("msg", "pressure information returned no 'some' data")
 			return ErrNoData
 		}
-		if vals.Full == nil {
+		if vals.Full == nil && res != "cpu" {
 			level.Debug(c.logger).Log("msg", "pressure information returned no 'full' data")
 			return ErrNoData
 		}