MdeModulePkg Variable: Before EndOfDxe, just record the current boot VarErrorFlag...

MdeModulePkg Variable: Before EndOfDxe, just record the current boot VarErrorFlag to local variable.

And leave the variable error flag in NV flash as the last boot variable error flag.
After EndOfDxe in InitializeVarErrorFlag (), the variable error flag in NV flash
will be initialized to this local current boot variable error flag.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16684 6f19259b-4bc3-4df7-8a09-765794883524