All harvesters: Remove output file if 0 rows retreived

[Joe-Heffer-Shef]

after completing harvester, use row count to determine if output file should be deleted

[Joe-Heffer-Shef]

• [x] aeroqual
• [x] earthsense
• [x] defra_sos_kvp
• [x] environment_agency_flood
• [x] airsonde