Add server-diagnostics metafile for api samples

Converts server-diagnostics api sample to create metafiles for
api sample docs. We use this to auto generate the specification
document.

Change-Id: I740aa597bab199d7571186c47ea15e31f960791e
Add _doc_post_server for ServersSampleBase

Add _doc_post_server function that support pass api_desc param.

Change-Id: I51332d970c00b232138653a603cf42bd971963f1
Adds security-groups metafiles for api samples

Converts security-groups api sample to create meta files for
api sample docs. We use this to auto generate the specification
document.

Change-Id: I2abdda6175ff3339077aff77f92d7f487850bf7a