Add additional explanation for apt install error

Signed-off-by: x893675 <[email protected]>

katacoda-scenarios/install-openfunction-on-kubernetes/step2.md

@@ -16,6 +16,24 @@ apt-get install -y --allow-change-held-packages kubelet=1.19.0-00 kubectl=1.19.0
 
 4.Upgrade kubernetes worker node: `ssh node01 "apt-get install -y kubelet=1.19.0-00 kubectl=1.19.0-00"`{{execute}}
 
+if this command print error message like:
+```
+E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)
+E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?
+```
+
+You can just try waiting before unlocking and run the command again.
+
+Or run commands:
+```
+ssh node01 "killall apt apt-get"
+# If none of the above works, remove the lock files. Run in terminal:
+ssh node01 "rm /var/lib/apt/lists/lock"
+ssh node01 "rm /var/cache/apt/archives/lock"
+ssh node01 "rm /var/lib/dpkg/lock*"
+ssh node01 "dpkg --configure -a"
+```
+
 5.Verify kubernetes status:
 ```
 kubectl version --short && \