gitlab-ci: fix workarounds for Ubuntu 16.04 in tests

The detection for Ubuntu 16.04 was broken. By now /etc/os-release
contains

    VERSION="16.04.7 LTS (Xenial Xerus)"

(cherry picked from commit 12e85574)
(cherry picked from commit 9f7736ea)

.gitlab-ci.yml

@@ -44,8 +44,8 @@ stages:
     - date '+%Y%m%d-%H%M%S'; dbus-uuidgen --ensure
     - date '+%Y%m%d-%H%M%S'; sed -i 's/^# \(pl_PL.UTF-8 .*\)$/\1/p' /etc/locale.gen ; true
     - date '+%Y%m%d-%H%M%S'; locale-gen pl_PL.UTF-8
-    - date '+%Y%m%d-%H%M%S'; grep -q "VERSION=.16.04.6 LTS" /etc/os-release && pip3 install meson==0.53.2
-    - date '+%Y%m%d-%H%M%S'; grep -q "VERSION=.16.04.6 LTS" /etc/os-release || pip3 install meson
+    - date '+%Y%m%d-%H%M%S'; grep -q "VERSION=.16.04.[0-9]\+ LTS" /etc/os-release && pip3 install meson==0.53.2
+    - date '+%Y%m%d-%H%M%S'; grep -q "VERSION=.16.04.[0-9]\+ LTS" /etc/os-release || pip3 install meson
     - date '+%Y%m%d-%H%M%S'; contrib/scripts/nm-ci-install-valgrind-in-ubuntu1604.sh
 
     # iproute2 5.2.0 on debian:sid causes our unit tests to fail.

contrib/scripts/nm-ci-install-valgrind-in-ubuntu1604.sh

@@ -13,7 +13,7 @@ set -exv
 #
 # Work around that by installing valgrind from bionic.
 
-grep -q 'PRETTY_NAME="Ubuntu 16.04.6 LTS"' /etc/os-release || exit 0
+grep -q 'PRETTY_NAME="Ubuntu 16.04.[0-9]\+ LTS"' /etc/os-release || exit 0
 dpkg -s valgrind | grep -q 'Version: 1:3.11.0-1ubuntu4.2$' || exit 0