Credentials should be zeroized immediately after connection is made

[BradleyBoutcher]

Summary

Credential zeroizing currently rests within a defer statement at internal/plugin/connectors/tcp/proxy_service.go:106. This statement will then only execute once the connection has been closed, or when a panic / error occurs early on and terminates the sequence. We should make sure that that statement is also executed immediately after the connection is made and the credentials are done being used.

Steps to Reproduce

Steps to reproduce the behavior:

1. Go to internal/plugin/connectors/tcp/proxy_service.go:106
2. Set a breakpoint after line 113, for example the logger statement on line 118
3. Verify that credentials have not been zeroized

Expected Results

When examining the value of backendCredentials after Connect has completed, if no error has occured, the value should be nil or empty.

Actual Results (including error logs, if applicable)

backendCredentials retains its value until the connection is terminated, by the process or by an error