[Ide] StatusProgressMonitor fixes

After the operation is completed, don't show error and warning dialogs
if it was cancelled.
[Ide] Previous solution loading fixes

Don't load the previously open solution if there is already an open solution.
It might happen if OSX sends an Open Document event while MD is
initializing.
[Ide] Allow opening two solutions at once

However, if the second solution has requested to close current, then cancel
the current load operation.

This fixes bug #24288 - 'Load previous solution on startup' option breaks
loading projects from the command line