PROBLEM:  (TKTR90018) (PATCH ID: OSF445-050)
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This patch fixes a "lock_terminate: lock held" panic when deleting
a process group.  An example stack trace:

        panic("lock_terminate: lock held")
        lock_terminate()
        pgdelete()
        pgrp_unref()
        pgrm()
        proc_teardown()
        waitf()
        wait4()
        syscall()
        _Xsyscall()