qrexec: in agent, use nonzero "fake" pid for existing process
qrexec: in agent, use nonzero "fake" pid for existing process

Because 0 means invalid entry.

marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,QubesOS/qubes-core-admin