Update build environments

- Older OS versions had older git versions
  which lack the dynamically-sized abbreviated
  object name mechanism, resulting in different
  build rev (git rev-parse --short HEAD) output
  for the same repo revision.

ClientLibrary/Dockerfile

@@ -2,7 +2,7 @@
 #
 # See README.md for usage instructions.
 
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 # Install system-level dependencies.
 ENV DEBIAN_FRONTEND=noninteractive

ConsoleClient/Dockerfile

@@ -2,7 +2,7 @@
 #
 # See README.md for usage instructions.
 
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 # Install system-level dependencies.
 ENV DEBIAN_FRONTEND=noninteractive

MobileLibrary/Android/Dockerfile

@@ -2,7 +2,7 @@
 #
 # See README.md for usage instructions.
 
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 # Install system-level dependencies.
 ENV DEBIAN_FRONTEND=noninteractive

Server/Dockerfile-binary-builder

@@ -1,4 +1,4 @@
-FROM alpine:3.4
+FROM alpine:3.10.2
 
 ENV GOLANG_VERSION 1.11.13
 ENV GOLANG_SRC_URL https://golang.org/dl/go$GOLANG_VERSION.src.tar.gz