Do not throw exception for invalid configuration file (#573)

Author: cheenamalhotra

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlAuthenticationProviderManager.NetCoreApp.cs

@@ -16,15 +16,15 @@ internal partial class SqlAuthenticationProviderManager
         static SqlAuthenticationProviderManager()
         {
             var activeDirectoryAuthNativeProvider = new ActiveDirectoryNativeAuthenticationProvider();
-            SqlAuthenticationProviderConfigurationSection configurationSection;
+            SqlAuthenticationProviderConfigurationSection configurationSection = null;
 
             try
             {
                 configurationSection = (SqlAuthenticationProviderConfigurationSection)ConfigurationManager.GetSection(SqlAuthenticationProviderConfigurationSection.Name);
             }
-            catch (ConfigurationErrorsException e)
+            catch (ConfigurationErrorsException)
             {
-                throw SQL.CannotGetAuthProviderConfig(e);
+                // Don't throw an error for invalid config files
             }
 
             Instance = new SqlAuthenticationProviderManager(configurationSection);

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlAuthenticationProviderManager.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
-using System.Configuration;
 using System.Linq;
 
 namespace Microsoft.Data.SqlClient