AFTER CRASH
Problem: The start_time member of trx_t structure is uninitialized in
         trx_create(), that is, at the time of transaction object creation.
         The start_time was initialized only at the start of transaction. 
         So after crash, start_time was taking the garbage value and while
         rollback is running in background for uncommited trx.

Fixed: Initialized the start_time member in trx_resurrect_*(), when trx
       is in either ACTIVE or PREPARED STATE. 

Approved by Jimmy (rb#4046).