utils: integrate comments from review

src/libknot/rrset-dump.c

src/libknot/rrset-dump.h

src/utils/common/exec.c

src/utils/common/params.c

src/utils/common/params.h

src/utils/dig/dig_params.c

src/utils/host/host_params.c

src/utils/nsec3hash/nsec3hash_main.c

src/utils/nsupdate/nsupdate_params.c