fsonetworkd: sharing plugin: use absolute paths for Posix.system
fsonetworkd: sharing plugin: use absolute paths for Posix.system

PATH might not be correct because fsonetworkd is being dbus-activated.

Signed-off-by: Klaus Kurzmann <c477880af38a6ff08996eb4cfb8b89c9ead729de@fluxnetz.de>

slyon/debian-fso-deviced,slyon/debian-fso-deviced,slyon/debian-fso-usaged,slyon/debian-fso-usaged