Add TeamCity metadata to that of an Instance Template

[mohsenrezaeithe]

This fixes https://youtrack.jetbrains.com/issue/TW-61898

Prior to the change the getInstanceBuilder was overwriting the Instance Template's Custom metadata with the setMetadata action.

This change pulls the configured Instance Template's information from GCP and adds the existing metadata to the custom TeamCity server ones before setting it for the new instance. In addition, a new method, getInstanceBuilder, also avoids overwriting the Availability policies in the newly created instance as well (values are inherited from the Instance Template).

All changes are tested in a staging environment with simulated workload.

[mohsenrezaeithe]

Here are some testing logs from the metadata capture:

[2019-09-16 21:45:04,607]   INFO [atcher-worker-1] - nnector.GoogleApiConnectorImpl - GCP get Instance Template: mythic-crane-708/global/instanceTemplates/teamcity-agent-poc-stg2-1567103841
[2019-09-16 21:45:04,740]   INFO [atcher-worker-1] - nnector.GoogleApiConnectorImpl - GCP Instance Template: com.google.cloud.compute.v1.InstanceTemplate$Builder@40ff690
[2019-09-16 21:45:04,740]   INFO [atcher-worker-1] - nnector.GoogleApiConnectorImpl - Instance Template properties captured from GCP: InstanceProperties{canIpForward=false, description=null, disks=[AttachedDisk{autoDelete=true, boot=true, deviceName=teamcity-agent-poc-stg2-1567103841, diskEncryptionKey=..., guestOsFeatures=null, index=0, initializeParams=AttachedDiskInitializeParams{description=null, diskName=null, diskSizeGb=300, diskType=pd-standard, labels=null, sourceImage=projects/..., sourceImageEncryptionKey=...}, interface2=null, kind=compute#attachedDisk, licenses=null, mode=READ_WRITE, source=null, type=PERSISTENT}], guestAccelerators=null, labels=null, machineType=n1-standard-4, metadata=Metadata{fingerprint=..., items=[Items{key=ENVIRONMENT_NAME, value=poc}, ...}, Items{key=startup-script, value=...}], kind=compute#metadata}, minCpuPlatform=null, networkInterfaces=[NetworkInterface{accessConfigs=null, aliasIpRanges=null, fingerprint=..., kind=compute#networkInterface, name=null, network=https://www.googleapis.com/compute/v1/projects/..., networkIP=null, subnetwork=https://www.googleapis.com/compute/v1/...}], scheduling=Scheduling{automaticRestart=true, nodeAffinities=null, onHostMaintenance=MIGRATE, preemptible=false}, serviceAccounts=[ServiceAccount{email=..., scopes=[...]}], tags=Tags{..., items=[...teamcity-agent]}}
[2019-09-16 21:45:04,745]   INFO [atcher-worker-1] - nnector.GoogleApiConnectorImpl - Creating an instance builder from merged metadata
[2019-09-16 21:45:04,747]   INFO [atcher-worker-1] - nnector.GoogleApiConnectorImpl - Creating instance from Instance Template: teamcity-agent-poc-stg2-1567103841

[mohsenrezaeithe]

@dimyriy @dmitry-treskunov have you had a chance to take a look at the changes? I've been running this live for a couple of weeks now with no issues, and I'd like to weigh the possibility of pulling this to the master.

[undimmable]

@mohsenrezaeithe, thank you for contributing! The pull request looks good to be merged into master overall except the comment about logging.

[mohsenrezaeithe]

@dimyriy thanks for reviewing! Good feedback, log details are removed.

[undimmable]

Thank you for contributing!