Ref: frysk-imports/tests/process/multi_child_parent_exec.c The parent proc needs to retain the child process and the child process it's tasks.
Testing: parent process A child threads A1 A2 A3 child threads A31 A32 When A execs then all of A2, A31, A32 tasks are tossed ending up back with just the main task. So this seems to be a variant of 2087. Testing: parent process A forks B B child threads B1 B2 When A execs then B, B1, B2 continue.
Added TestExec.java (testAttachedMultipleParentExec)