Command line/RAPI support for --no-name-check

This patch adds --no-name-check to gnt-instance add and gnt-backup
import. This is opposite to the opcode parameter (name_check) as it is
similar to ip_check and start.

It also adds it to RAPI and gnt-instance batch-create as a parameter in
the input (JSON-formatted) file.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>