ANALYSIS:
=========
During Bootstrap, while executing the statements from sql
file passed to the init-file server option, transaction
mem_root was being freed for every statement. This creates
an issue with multi statement transactions especially when a
statement in the transaction has to access the memory used
by the previous statement in the transaction.

FIX:
====
Transaction mem_root is freed whenever a transaction is
committed or rolled-back. Hence explicitly freeing it is not
necessary in the bootstrap implementation.

Change-Id: I40f71d49781bf7ad32d474bb176bd6060c9377dc