1) Fix the bug that Variable Cache Search does not be protected by lock during boot...

1) Fix the bug that Variable Cache Search does not be protected by lock during boot time. It potentially results in the info from GetVariable() is not correct.
2) Check the integrity of Variable header. In original implementation, if not whole header is correct, then the variable will be treat as invalid. typically, if the NameSize has been programed but the DataSize not, then the variable storage would failed to set new variable.
3) Change the Variable Header Alignment from 1 to 4 bytes on x86. It avoids the DataSize or NameSize cross two blocks. For example, in original implementation, if the NameSize crosses two block, when the FLASH manipulation is interrupted after programed HSB of NameSize and prior to program LSB of NameSize on next block, then the invalid variable header will result in the Variable Storgae broken.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4538 6f19259b-4bc3-4df7-8a09-765794883524