tgtadm: Correct mode names in the option error message

When an error option is specified for some mode and operation,
tgtadm outputs an error message which contains the mode name.
But some of the mode names are obviously wrong so the patch fixes
them.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
tgtadm: display unsupported operation name explicitly

When we specify an unsupported operation type for some mode,
tgtadm will display the error message which contains the
unsupported operation type value. The patch changes to
display the operation name which is more explicit. Also
change the word 'option' to 'operation'.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>