src/libpcp/src/derive_fetch.c: small tweak when lookup up instance names
src/libpcp/src/derive_fetch.c: small tweak when lookup up instance names

Setting the time origin is only valid for archives ... for host
contexts this generates PM_ERR_IPC from pmcd.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp