Add "ignore-ipolicy" option to gnt-instance grow-disk

Unless the option is given, growing disks outside the ipolicy limits
will fail.

Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>
Add a helper function for checking the disk size ipolicy

The function only checks the disk-related parameters: The disk sizes
(and their count) and the disk template.

Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>
Test function ComputeIPolicyDiskSizesViolation

The class tests basic properties of the function.

Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>
Check disk size ipolicy during "gnt-instance grow-disk"

If a new disk size doesn't fit the ipolicy and --ignore-ipolicy is
given, just log warnings. If it's not, fail the operation.

Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>