Fix build.extra_hosts list format

Signed-off-by: Anca Iordache <[email protected]>

compose/service.py

@@ -1877,8 +1877,10 @@ class _CLIBuilder:
         command_builder.add_arg("--isolation", isolation)
 
         if extra_hosts:
-            for host, ip in extra_hosts.items():
-                command_builder.add_arg("--add-host", "{}:{}".format(host, ip))
+            if isinstance(extra_hosts, dict):
+                extra_hosts = ["{}:{}".format(host, ip) for host, ip in extra_hosts.items()]
+            for host in extra_hosts:
+                command_builder.add_arg("--add-host", "{}".format(host))
 
         args = command_builder.build([path])