Add changelog for LKE 1.7.2

Author: thorner

src/content/changelog/lke-1-7-2.md

@@ -0,0 +1,15 @@
+---
+title: Linode Kubernetes Engine v1.7.2
+date: 2020-09-01T05:00:00.000Z
+version: 1.7.2
+changelog:
+  - Linode Kubernetes Engine
+---
+
+### Added
+
+* Add mitigation for CVE-2020-8558 on node initialization. Users should recycle
+  their nodes for these changes to apply.
+* Upgrade the control planes to the latest patch version available: v1.15.12,
+  v1.16.14, and v1.17.11.
+