Add zsh completion for etwlogs and gcplogs log drivers

Signed-off-by: Steve Durrheimer <s.durrheimer@gmail.com>

contrib/completion/zsh/_docker

@@ -528,7 +528,7 @@ __docker_subcommand() {
         "($help)--ipc=[IPC namespace to use]:IPC namespace: "
         "($help)*--link=[Add link to another container]:link:->link"
         "($help)*"{-l=,--label=}"[Container metadata]:label: "
-        "($help)--log-driver=[Default driver for container logs]:Logging driver:(json-file syslog journald gelf fluentd awslogs splunk none)"
+        "($help)--log-driver=[Default driver for container logs]:Logging driver:(awslogs etwlogs fluentd gcplogs gelf journald json-file none splunk syslog)"
         "($help)*--log-opt=[Log driver specific options]:log driver options:__docker_log_options"
         "($help)--mac-address=[Container MAC address]:MAC address: "
         "($help)--name=[Container name]:name: "
@@ -669,7 +669,7 @@ __docker_subcommand() {
                 "($help)--ipv6[Enable IPv6 networking]" \
                 "($help -l --log-level)"{-l=,--log-level=}"[Logging level]:level:(debug info warn error fatal)" \
                 "($help)*--label=[Key=value labels]:label: " \
-                "($help)--log-driver=[Default driver for container logs]:Logging driver:(json-file syslog journald gelf fluentd awslogs splunk none)" \
+                "($help)--log-driver=[Default driver for container logs]:Logging driver:(awslogs etwlogs fluentd gcplogs gelf journald json-file none splunk syslog)" \
                 "($help)*--log-opt=[Log driver specific options]:log driver options:__docker_log_options" \
                 "($help)--mtu=[Network MTU]:mtu:(0 576 1420 1500 9000)" \
                 "($help -p --pidfile)"{-p=,--pidfile=}"[Path to use for daemon PID file]:PID file:_files" \