Fix flashcache_load getting cachedev from argv when using flags

The cachedev parameter is in position 3 when no flags specificed.
When -v is used then cachedev will be in position 4.

Signed-off-by: Roi Dayan <roid@mellanox.com>
Merge pull request #104 from roidayan/fix_flashcache_load

Fix flashcache_load getting cachedev from argv when using flags