Enforce non-interactive package installation in CI (#701)

Fixes issue with failing ubuntu:focal jobs due to tzdata package asking
user to provide information about location and timezone.

Author: mliszcz

.travis/debian10/Dockerfile

@@ -6,6 +6,8 @@ ARG APP_GID=2000
 
 MAINTAINER TANGO Controls team <tango@esrf.fr>
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN apt-get update && apt-get install -y \
   apt-utils                              \
   build-essential                        \

.travis/debian8/Dockerfile

@@ -6,6 +6,8 @@ ARG APP_GID=2000
 
 MAINTAINER TANGO Controls team <tango@esrf.fr>
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN sed -i '/jessie-updates/d' /etc/apt/sources.list  # Now archived
 
 RUN apt-get update && apt-get install -y \

.travis/debian9/Dockerfile

@@ -6,6 +6,8 @@ ARG APP_GID=2000
 
 MAINTAINER TANGO Controls team <tango@esrf.fr>
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN apt-get update && apt-get install -y \
   apt-utils                              \
   build-essential                        \

.travis/gcc-latest/Dockerfile

@@ -6,6 +6,8 @@ ARG APP_GID=2000
 
 MAINTAINER TANGO Controls team <tango@esrf.fr>
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN apt-get update && apt-get install -y \
   apt-utils                              \
   build-essential                        \

.travis/llvm-latest/Dockerfile

@@ -8,6 +8,8 @@ ARG APP_GID=2000
 
 MAINTAINER TANGO Controls team <tango@esrf.fr>
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN apt-get update && apt-get install -y \
   apt-utils                              \
   build-essential                        \

.travis/ubuntu-20.04/Dockerfile

@@ -6,6 +6,8 @@ ARG APP_GID=2000
 
 MAINTAINER TANGO Controls team <tango@esrf.fr>
 
+ENV DEBIAN_FRONTEND=noninteractive
+
 RUN apt-get update && apt-get install -y \
   apt-utils                              \
   build-essential                        \