ZWEAM511E message is misleading

[CarsonCook]

Describe the bug
The ZWEAM511E message says certificates aren't trusted, but this is inaccurate. For example,

"messageNumber": "ZWEAM511E",
    "messageContent": "The certificate of the service accessed using URL '/zss/api/v1/unixfile/contents/%2Fu%2F/carson' is not trusted by the API Gateway: java.net.SocketException: Connection reset",

was logged, when the issue was actually around a configured IP address. This message is also logged when certificate validation is turned off, which makes no sense.

Steps to Reproduce

1. Start Zowe with certificates not being verified and ZWED_agent_http_ipAddresses=0.0.0.0 -> http instead of https will mislead ZSS
2. Run a request via APIML that goes to ZSS
3. See the error message that the certificate isn't trusted

Expected behavior
A message that isn't misleading, ideally it can point to specific details, but the nature of this type of error is it's going to be various problems.

https://github.com/zowe/api-layer/wiki/Issue-management

[CarsonCook]

This message is returned when an SSLException is thrown. There can be a variety of causes, making it difficult to capture a good error message. Some options:

1. Look in the thrown exception message for text indicating different types of problems that can cause SSLException to be thrown. This may be brittle and flaky, and would still require a generic message if none of the hardcoded checks are found.

2. Change the error message to a generic message that there's an SSL error. This won't mislead anyone, but also won't help anyone.

3. Add potential causes to the error message itself (it already lists two possible causes). This is essentially option 1, but easier to maintain as it doesn't involve java code changes.

4. Potentially in addition to other options, add to the error message an indication of how to view the actual error message as the thrown exception message is logged in debug mode.

5. Potentially in addition to other options, add debug logging to indicate the state of the GW - e.g. if certs are being validated (indicating cert trust is not an issue)