CSharpLanguageServer: Wait for indexing to complete

resolving issues pertaining to retrievals not working correctly initially

Fixes #814

test/solidlsp/csharp/test_csharp_basic.py

@@ -119,13 +119,9 @@ class TestCSharpLanguageServer:
 
         # Check that we have references from both files
         assert any("Program.cs" in ref_file for ref_file in ref_files), "Should find reference in Program.cs"
-        # TODO: The assertion below fails randomly. Try to fix this. GitHub issue #814
-        #   In CI, it sometimes passed; on my local machine (opcode81), it seems to fail consistently.
-        """
         assert any(
             os.path.join("Models", "Person.cs") in ref_file for ref_file in ref_files
         ), "Should find reference in Models/Person.cs where Calculator.Subtract is called"
-        """
 
         # check for a second time, since the first call may trigger initialization and change the state of the LS
         refs_second_call = language_server.request_references(file_path, sel_start["line"], sel_start["character"] + 1)