Relax activate/deactivate error conditions
Relax activate/deactivate error conditions

Treat activating an already active port and deactivating an already
inactive port as harmless no-ops. Specifying a port or version of a
port that isn't installed is still an error.

Fixes: https://trac.macports.org/ticket/56817

macports/macports-base,neverpanic/macports-base,neverpanic/macports-base,macports/macports-base,danchr/macports-base,danchr/macports-base