src/libpcp/src/pmns.c: small strncpy() -> memmove() change
src/libpcp/src/pmns.c: small strncpy() -> memmove() change

Fixes Fedora 29 gcc warning, and is strictly speaking more correct
(we're building a PMNS name from leaf to root here, so the result
is not a string until we're done).

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