Update docs on ssd disk initialization

+ change number of linux agents

+ removed outputs in job analysis

+ updated windows image

.gitignore

@@ -6,3 +6,4 @@ __pycache__/
 containers/workspace
 **/.DS_Store
 **/.ipynb_checkpoints
+scripts/buildkite/cache.json

docs/playbooks.md

@@ -117,7 +117,7 @@ To spawn a new windows agent:
 1. In the RDP session: run these commands in the CMD window under Administrator to bootstrap the Windows machine:
     ```powershell 
     Invoke-WebRequest -uri 'https://raw.githubusercontent.com/google/llvm-premerge-checks/master/scripts/windows_agent_bootstrap.ps1' -OutFile c:\windows_agent_bootstrap.ps1
-    c:/windows_agent_bootstrap.ps1
+    c:/windows_agent_bootstrap.ps1 -ssd
     ```
     Ignore the pop-up to format the new disk and wait for the machine to reboot.
     

kubernetes/buildkite/deployment.yaml

@@ -18,7 +18,7 @@ metadata:
   name: premerge-debian
   namespace: buildkite
 spec:
-  replicas: 5
+  replicas: 4
   template:
     metadata:
       labels:

kubernetes/windows_agent_create.sh

@@ -30,6 +30,6 @@ gcloud beta compute instances create "${NAME}" \
   --zone="${GCP_ZONE}" \
   --machine-type=n1-standard-16 \
   --local-ssd=device-name=local-ssd-0 \
-  --image=windows-server-2019-dc-for-containers-v20200512 \
+  --image=windows-server-2019-dc-for-containers-v20200609 \
   --image-project=windows-cloud \
   --boot-disk-size=100GB