Add uefi boot mode support in IloVirtualMediaIscsiDeploy

The following functionality need to be added in iLO driver:
  - Add set_boot_mode function to iLO driver to switch between
    bios and uefi boot modes.
  - Validate boot_mode for IloVirtualMediaIscsiDeploy driver.

Change-Id: Ic8496a2d97aab6634b573c85d379b446c49e04b9
Implements: blueprint uefi-boot-for-ironic
Merge "Add uefi boot mode support in IloVirtualMediaIscsiDeploy"