monitor size of /tmp

OpenBMC application use /tmp for a variety of reasons. If /tmp becomes
full, then certain applications will start to fail (in very undefined
ways).

/tmp uses a tmpfs filesystem that is backed by BMC memory. Just
monitoring BMC memory is not enough though because by default, only 50%
of memory is allowed to be used by /tmp.

This commit adds in a default to monitor /tmp and log to the journal if
it sees /tmp exceed 85% usage. This will at least offer a clue to users
when debugging issues.

Tested:
- Tested as a part of the following commit:
  https://gerrit.openbmc.org/c/openbmc/openbmc/+/56065

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I1355f0d29a0b7a0840075561069d4ec7d3b27672
diff --git a/bmc_health_config.json b/bmc_health_config.json
index 025eadf..b969676 100644
--- a/bmc_health_config.json
+++ b/bmc_health_config.json
@@ -44,5 +44,19 @@
             "Target": ""
         }
     }
+  },
+  "Storage_TMP" : {
+    "Path" : "/tmp",
+    "Frequency" : 1,
+    "Window_size": 120,
+    "Threshold":
+    {
+        "Critical":
+        {
+            "Value": 85.0,
+            "Log": true,
+            "Target": ""
+        }
+    }
   }
 }