feat(scanner): Don't scan and log if we are below sapling height #653

Job	Run time
Build CI Docker / Build images	11m 7s
Test all	19m 45s
Test checkpoint sync from empty state	11m 23s
Test with fake activation heights	8m 16s
Test integration with lightwalletd	11m 14s
Test CI default Docker config file / Test default-conf in Docker	2m 25s
Test CI testnet Docker config file / Test testnet-conf in Docker	2m 32s
Test CI custom Docker config file / Test custom-conf in Docker	1m 20s
Open or update issues for main branch failures	0s
	1h 8m 2s

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