[BUG] ETH gas price sustain at very high doesn't come down

Here is how the gas price work on ETH at the moment, bifrost will keep track of the following few informations

1. Current gas price report to THORNode
2. Gas price in the last 20 blocks

When report gas price to thornode , bifrost do the following

1. Get the highest gas price in the last 20 blocks
2. Compare the highest gas price against current gas price report to THORNode
3. if the highest gas price is higher than current gas price , report to THORNode
4. If the highest gas price is lower than half of current gas price , ignore

item 4 above cause an issue on an edge case, when ETH gas price spike quickly , the network will be able to follow it , if the gas price spike , and then drop significantly , then the network will not follow