illumos gate

Related to #12046 ...

The pair of prdgetfdinfosize() and prdgetfdinfo() perform operations with vnodes, but their callers first release the hold on the inspected-process's file-table entry. This involves releasing-and-re-holding the process lock, which may enable a process thread to close the file, deleting vnode data that the aforementioned functions' subsequent calls ASSERT is there.

Short of refactoring how procfs does and does not obtain FDINFO, a tested course of action is to call the aforementioned functions PRIOR to releasing the file-table entry.