libct/cg/sd/systemdVersion: don't return error
libct/cg/sd/systemdVersion: don't return error

As the caller of this function just logs the error, it does not make
sense to pass it. Instead, log it (once) and return -1.

This is a preparation for the second user.

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

dqminh/runc,estesp/runc,estesp/runc,kolyshkin/runc,estesp/runc,dqminh/runc,opencontainers/runc,kolyshkin/runc,dqminh/runc,rhatdan/runc,opencontainers/runc,opencontainers/runc,rhatdan/runc,kolyshkin/runc,opencontainers/runc,rhatdan/runc,dqminh/runc,rhatdan/runc,kolyshkin/runc