Provide monitor & ask for cancellation on the monitor in case API
analysis job runs at same time a baseline is disposed.

Change-Id: I0fc91b0252eaf2a7b0275c84b7245a1804f3bfee
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/pde/eclipse.pde.ui/+/189733
Tested-by: PDE Bot <pde-bot@eclipse.org>