update os values in integration test

Author: Codeslayer666

test/helpers/infra.py

@@ -40,7 +40,7 @@
         zone=ZONE.London,
         password_delivery='none',
         storage_devices=[
-            Storage(os='CentOS 7.0', size=10),
+            Storage(os='CentOS 7.6', size=10),
             Storage(size=10),
         ],
         login_user=login_user_block('testuser', ['ssh-rsa AAAAB3NzaC1yc2EAA[...]ptshi44x user@some.host'], True),
@@ -53,7 +53,7 @@
         zone=ZONE.London,
         password_delivery='none',
         storage_devices=[
-            Storage(os='Debian 7.8', size=30)
+            Storage(os='Debian 10.0', size=30)
         ],
         login_user=login_user_block('testuser', ['ssh-rsa AAAAB3NzaC1yc2EAA[...]ptshi44x user@some.host'], True),
         )

upcloud_api/cloud_manager/server_mixin.py

@@ -105,10 +105,9 @@ def create_server(self, server):
           (id is a running starting from 1)
         - tier defaults to maxiops
         - valid operating systems are:
-          "CentOS 6.5", "CentOS 7.0"
-          "Debian 7.8"
+          "CentOS 6.10", "CentOS 7.6"
           "Ubuntu 12.04", "Ubuntu 14.04"
-          "Windows 2003","Windows 2008" ,"Windows 2012"
+          "Windows 2012", "Windows 2016"
         """
         if isinstance(server, Server):
             body = server.prepare_post_body()