Estafette-gke-node-pool-shifter v1.2.4

Resolved issues (3)

• Improve liveness probe to avoid frequent restarts. #27, @JorritSalverda
• Build with golang 1.13.7. #26, @JorritSalverda
• Build with golang 1.13.6. #24, @JorritSalverda

See milestone 1.2.4 for more details.