fix exec3_serial "serial starting" log

[sudeepdino008]

from and to are currently same:

INFO[02-12|10:38:04.617] [6/8 Execution] serial starting          from=29542423 to=29542422 initialTxNum=202940290 initialBlockTxOffset=0 lastFrozenStep=128 initialCycle=true isForkValidation=false isBlockProduction=false
INFO[02-12|10:38:24.619] [6/8 Execution] serial executed          blk=29545691 blks=3269 blk/s=163 txs=31.07k tx/s=1.55k gas/s=264.98M tgas/s=0(0) aratio=0.0 tdur=0s trdur=0s(0.00%) rd=0 rd/s=0 buf=166.3MB/512.0MB bdur=4ms ucgas=5.30G alloc=8.1GB sys=24.3GB isForkValidation=false isBlockProduction=false isApplyingBlocks=true
INFO[02-12|10:38:44.620] [6/8 Execution] serial executed          blk=29549581 blks=3890 blk/s=194 txs=31.54k tx/s=1.57k gas/s=280.92M tgas/s=0(0) aratio=0.0 tdur=0s trdur=0s(0.00%) rd=0 rd/s=0 buf=281.5MB/512.0MB bdur=4ms ucgas=1

• also simplified the if condition when log is printed