VNC harcoded server name removed

  VNC server can be other than WebSockify, so there is a need to
  configure it once in a while for various deployments

    - added config option
    - updated test

Change-Id: I938bae347eaa9fcf76e4118188b325ba6d3efa77
Closes-Bug: #1748339
diff --git a/releasenotes/notes/vnc-hardcoded-server-name-removed-6f8d1e90a175dc08.yaml b/releasenotes/notes/vnc-hardcoded-server-name-removed-6f8d1e90a175dc08.yaml
new file mode 100644
index 0000000..0da2ddc
--- /dev/null
+++ b/releasenotes/notes/vnc-hardcoded-server-name-removed-6f8d1e90a175dc08.yaml
@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    New string configuration option ``vnc_server_header`` is added
+    to ``compute-feature-enabled`` section. It offers to provide VNC server
+    name that is to be expected in the responce header. For example, obvious
+    at hand names is 'WebSockify', 'nginx'.
+fixes:
+  - |
+    Fix VNC server response header issue when it is behind reverse proxy