PATCH: Handle the cross type of debugging (context & in-context) on same function at the same time

Hi Dave,

During testing of the debugger, our (EnterpriseDB's) QA found an issue.

Please found the scenario:

1. Start a global (in-context) debugging session on a function (by clicking on Debugging -> Set breakpoint)

2. And, then start the direct debugging session on the same function (by clicking on Debugging -> Debug)

As the global debugging session is already waiting for this function, the debugging will start in that environment.

Now - if we try to close the direct debugging session, pgAdmin will throw an error saying pldbg_abort_target() does not exist.

Because - the direct debugging session has not yet started, we do not have the session-id in that environment.

Hence, we need to inform only the execution connection to get terminated, and that resolved the issue.

But - other problem came up, when we once again close the direct debugging session. As we're already in the closing operation,

it once again try to close the execution connection, which is not write and this time the pgAdmin became unresponsive.

In order to resolve this problem, we need to introduce the flag to let know the debugger frame that we're already in process of stopping

the session.

Please find the patch, which will resolve this issue.