Change platform memory usage instance type to 'memory'

The platform memory data-set type is currently set to 'percent'.

It is possible to over subscribe platform memory usage to more
than 100%.

Collectd drops sample values that are greater than 100 when its
data-set type is 'percent'. Collectd considers a percent value
greater than 100 to be an invalid value.

This update changes the data-set type for platform memory usage
from 'percent' to 'memory' to allow memory usage values greater
than 100 to be handled.

Test Plan:

PASS: Verify that platform memory overage alarm value is reported
             as the 'actual' value in the alarm Reason Text.
PASS: Verify platform memory usage values that exceed the major
             threshold are alarmed 'major'.
PASS: Verify platform memory usage values that exceed the critical
             threshold are alarmed 'critical', even if the
             debounced value exceeds 100.
PASS: Verify ridiculously large values are still alarmed and that
             value is still included in the alarm Reason Text.

Change-Id: I7189671e20c92656f820fda74c4871504d89e73a
Closes-Bug: 1940875
Signed-off-by: Eric MacDonald <eric.macdonald@windriver.com>

collectd-extensions/src/memory.conf

@@ -8,7 +8,7 @@
 
 <Plugin "threshold">
   <Plugin "memory">
-    <Type "percent">
+    <Type "memory">
       Instance "used"
       Persist true
       PersistOK true

collectd-extensions/src/memory.py

@@ -512,7 +512,7 @@ def read_func():
     # Dispatch overall platform usage percent value
     if obj.platform_memory_percent > 0.0:
         val = collectd.Values(host=obj.hostname)
-        val.type = 'percent'
+        val.type = 'memory'
         val.type_instance = 'used'
         val.plugin = 'memory'
         val.plugin_instance = 'platform'