[ethereum/go-ethereum] geth automatically invalidate transactions ? (#17455)

Hi there,

I use the geth for a pool. some times I can see it show out some transactions log. But I never sent a command to the geth.

#### System information

Geth version: `geth 1.8.13-stable-225171a4`
OS & Version: Ubuntu 16.04 LTS

here is the logs:

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INFO [08-21|05:54:51.409] Commit new mining work number=6183720 txs=136 uncles=0 elapsed=1.426s
INFO [08-21|05:55:10.009] Imported new chain segment blocks=1 txs=135 mgas=7.984 elapsed=190.508ms mgasps=41.911 number=6183720 hash=91f002…e646bd cache=535.78mB
INFO [08-21|05:55:11.399] Commit new mining work number=6183721 txs=125 uncles=0 elapsed=1.389s
INFO [08-21|05:55:15.771] Imported new chain segment blocks=1 txs=114 mgas=7.993 elapsed=269.889ms mgasps=29.616 number=6183721 hash=261fec…1ff16d cache=536.35mB
INFO [08-21|05:55:17.384] Commit new mining work number=6183722 txs=91 uncles=0 elapsed=1.613s
INFO [08-21|05:55:23.779] Submitted transaction fullhash=0xce7c8fb177f807e6f9aead246f9ab4fe4ac28afb350c14d9f9abb1f2041a43f0 recipient=0x91159390631ed2bfc6967695be85deE3Be022cE3
INFO [08-21|05:55:23.851] Submitted transaction fullhash=0xa24a42a2152b09b34f2e0f54905f7f7a113e81f45049e7a527c656ed50f725b3 recipient=0xc0e4F45b828Aa4aA628e897e5DA38d9dC72C2257
INFO [08-21|05:55:23.907] Submitted transaction fullhash=0x9f052faf4b155bd08fe93f83da49fbee7891da4f197793adb9ece46c57c9559a recipient=0xE534619dEFDBF0cAf673b8AbF7158714F5BD4bd9
INFO [08-21|05:55:23.949] Submitted transaction fullhash=0x99c38235e52513b37a649fb8d51677d3d0faffb77ff00b9c7b92ad2e0f43265b recipient=0xF3e014fE81267870624132ef3A646B8E83853a96
INFO [08-21|05:55:23.996] Submitted transaction fullhash=0xf3e6ee06c75997de3ddce62bf398d963bffd094048f9d25d8a9cf4d6b417963c recipient=0x358D12436080a01A16f711014610F8a4c2C2d233
INFO [08-21|05:55:41.748] Imported new chain segment blocks=1 txs=72 mgas=7.985 elapsed=351.286ms mgasps=22.730 number=6183722 hash=4d344a…15edba cache=536.21mB
INFO [08-21|05:55:43.503] Commit new mining work number=6183723 txs=156 uncles=0 elapsed=1.754s
INFO [08-21|05:56:24.530] Imported new chain segment blocks=1 txs=154 mgas=8.001 elapsed=293.789ms mgasps=27.232 number=6183723 hash=9d4986…6bc0e0 cache=536.24mB
INFO [08-21|05:56:26.088] Commit new mining work number=6183724 txs=115 uncles=0 elapsed=1.557s
INFO [08-21|05:56:44.211] Imported new chain segment blocks=1 txs=154 mgas=7.982 elapsed=809.006ms mgasps=9.867 number=6183724 hash=4fedda…5b3533 cache=535.73mB
INFO [08-21|05:56:45.729] Commit new mining work number=6183725 txs=92 uncles=0 elapsed=1.518s
INFO [08-21|05:56:48.905] Imported new chain segment blocks=1 txs=90 mgas=7.939 elapsed=1.471s mgasps=5.394 number=6183725 hash=fd6f13…f99b19 cache=536.19mB
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