Change SysfsValue to HWMon::attribute

There is no need to read all of the files for every value we want.

Change-Id: I307ead2177c5fce130aa653d5098663063d71cad
diff --git a/tests/hardware_ietf-hardware.cpp b/tests/hardware_ietf-hardware.cpp
index 9f70663..23d6824 100644
--- a/tests/hardware_ietf-hardware.cpp
+++ b/tests/hardware_ietf-hardware.cpp
@@ -45,14 +45,10 @@
     };
     FAKE_HWMON(fans, attributesHWMon);
 
-    attributesHWMon = {{"temp1_input", 30800}};
-    FAKE_HWMON(sysfsTempFront, attributesHWMon);
-    attributesHWMon = {{"temp1_input", 41800}};
-    FAKE_HWMON(sysfsTempCpu, attributesHWMon);
-    attributesHWMon = {{"temp1_input", 39000}};
-    FAKE_HWMON(sysfsTempMII0, attributesHWMon);
-    attributesHWMon = {{"temp1_input", 36000}};
-    FAKE_HWMON(sysfsTempMII1, attributesHWMon);
+    REQUIRE_CALL(*sysfsTempFront, attribute("temp1_input")).RETURN(30800);
+    REQUIRE_CALL(*sysfsTempCpu, attribute("temp1_input")).RETURN(41800);
+    REQUIRE_CALL(*sysfsTempMII0, attribute("temp1_input")).RETURN(39000);
+    REQUIRE_CALL(*sysfsTempMII1, attribute("temp1_input")).RETURN(36000);
 
     attributesEMMC = {{"life_time"s, "40"s}};
     FAKE_EMMC(emmc, attributesEMMC);