[IA64] Fix incorrect NVRAM saving if domain is destroyed by config error

[IA64] Fix incorrect NVRAM saving if domain is destroyed by config error

Nvram saving is always executed even if a domain is destroyed by a
configuration parameter error.  In this case, Nvram saving function
will get a bad address for the NVRAM data and save garbage into the
NVRAM file. Configuring a wrong vif parameter can expose this issue.

This patch fixes the issue by adding an address check function in
NVRAM saving path.

Signed-off-by: Zhang Xin <xing.z.zhang@intel.com>