Mutual close gets stuck if an `UpdateFee` arrives at a bad time

[pm47]

Because this will create a new sig/rev/sig/rev cycle that is not properly handled.

2023-08-20 18:05:05,524 INFO  f.a.e.i.Peer n:030000 c:cccccc - IN msg=Shutdown(cccccc,ByteVector(34 bytes, 0x0020c0d79b262ff4e9e1569fd6c3de226d5a45c22c218e2583ad494d8677eb1d683c),TlvStream(Set(ChannelDataTlv(ByteVector(1602 bytes, #-1995771010))),Set()))
2023-08-20 18:05:05,524 INFO  f.a.e.c.fsm.Channel n:030000 c:cccccc - using finalScriptPubkey=ByteVector(22 bytes, 0x0014aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)
2023-08-20 18:05:05,535 INFO  f.a.e.i.Peer n:030000 c:cccccc - OUT msg=Shutdown(cccccc,ByteVector(22 bytes, 0x0014aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa),TlvStream(Set(),Set()))
2023-08-20 18:05:05,535 INFO  f.a.eclair.router.Router SYN n:030000 c:cccccc - removing private local channel and channel_update for channelId=cccccc localAlias=0x68358f8ceefdce
2023-08-20 18:05:06,141 INFO  f.a.e.i.Peer n:030000 c:cccccc - IN msg=RevokeAndAck(cccccc,<private_key>,02f578ee049781f380dd3b69592f01d32a4a4fe18bad5fe70d6eb5b25387c5cf83,TlvStream(Set(ChannelDataTlv(ByteVector(1640 bytes, #-831406130))),Set()))
2023-08-20 18:05:39,142 INFO  f.a.e.i.Peer n:030000 c:cccccc - OUT msg=UpdateFee(cccccc,1799 sat/kw,TlvStream(Set(),Set()))
2023-08-20 18:05:39,156 INFO  f.a.e.i.Peer n:030000 c:cccccc - OUT msg=CommitSig(cccccc,e25b4ed748624b3a6fcec64b4b8fa966f70a2c2a4eca2ea7d9d8f272b69c318951fa9acc3acde90ef3a561d6a03098d6940e8b37b7af1c0a4355b553aa466336,List(),TlvStream(Set(),Set()))
2023-08-20 18:06:01,859 INFO  f.a.e.i.Peer CON n:030000 c:cccccc - OUT msg=ChannelReestablish(cccccc,2,2,<private_key>,022901a21d2f0075c80b98ec3efe65651e5b7618517f8d02e98be5c69f22343dbd,TlvStream(Set(ChannelDataTlv(ByteVector(1640 bytes, #-831406130))),Set()))
2023-08-20 18:06:02,533 INFO  f.a.e.i.Peer CON n:030000 c:cccccc - IN msg=ChannelReestablish(cccccc,3,1,<private_key>,02fcf5a32e514ff6b23f600d6fbf698120a3896f0d7638769b22bb9b77b26f290a,TlvStream(Set(),Set()))
2023-08-20 18:06:02,534 INFO  f.a.e.i.Peer n:030000 c:cccccc - OUT msg=UpdateFee(cccccc,1799 sat/kw,TlvStream(Set(),Set()))
2023-08-20 18:06:02,534 INFO  f.a.e.i.Peer n:030000 c:cccccc - OUT msg=CommitSig(cccccc,e25b4ed748624b3a6fcec64b4b8fa966f70a2c2a4eca2ea7d9d8f272b69c318951fa9acc3acde90ef3a561d6a03098d6940e8b37b7af1c0a4355b553aa466336,List(),TlvStream(Set(),Set()))
2023-08-20 18:06:02,534 INFO  f.a.e.i.Peer n:030000 c:cccccc - OUT msg=Shutdown(cccccc,ByteVector(22 bytes, 0x0014aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa),TlvStream(Set(),Set()))
2023-08-20 18:06:02,550 INFO  f.a.e.i.Peer n:030000 c:cccccc - IN msg=Shutdown(cccccc,ByteVector(34 bytes, 0x0020c0d79b262ff4e9e1569fd6c3de226d5a45c22c218e2583ad494d8677eb1d683c),TlvStream(Set(ChannelDataTlv(ByteVector(1553 bytes, #-261787000))),Set()))
2023-08-20 18:06:02,550 WARN  f.a.e.c.fsm.Channel n:030000 c:cccccc - unhandled event Shutdown(cccccc,ByteVector(34 bytes, 0x0020c0d79b262ff4e9e1569fd6c3de226d5a45c22c218e2583ad494d8677eb1d683c),TlvStream(Set(ChannelDataTlv(ByteVector(1553 bytes, #-261787000))),Set())) in state SHUTDOWN