MdeModulePkg SetupBrowserDxe: Save global variable values before nest function called.

MdeModulePkg SetupBrowserDxe: Save global variable values before nest function called.

The SendForm function can be called nest in it. This function also uses some global variables. So we must save global variable values before it been called again.

Checked in the missing change for gBrowserFormSetList.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18681 6f19259b-4bc3-4df7-8a09-765794883524