Merge branch 'jmd-update-docker-inspect-commands-to-avoid-errors' into 'master'

Replace docker inspect with list filter

See merge request gitlab-org/gitlab-qa!1013

lib/gitlab/qa/docker/engine.rb

@@ -119,19 +119,11 @@ module Gitlab
         end
         def container_exists?(name)
-          Docker::Command.execute("container inspect #{name}")
-        rescue Docker::Shellout::StatusError
-          false
-        else
-          true
+          !Docker::Command.execute("container list --all --format '{{.Names}}' --filter name=^#{name}$").empty?
         end
         def network_exists?(name)
-          Docker::Command.execute("network inspect #{name}")
-        rescue Docker::Shellout::StatusError
-          false
-        else
-          true
+          !Docker::Command.execute("network list --format '{{.Name}}' --filter name=^#{name}$").empty?
         end
         def network_create(name)