Calling getBlock in BlockBuffer constructor 2 is unnecessary

[SaintNerevar]

The design stipulates that any get/set methods accessing disk blocks must call BlockBuffer::getBufferPtr() which calls getBlock(). So, not calling getBlock() in the constructor simply delays copying the block into the buffer until it is actually needed i.e to access the blocks data.

[gokulsreekumar]

• getBlock() removed and loadBlockAndGetBufferPtr() function introduced