[WANTED FEATURE]Retain extracted products for dedup after GUNWs removed

[rzinke]

Is your feature request related to a problem? Please describe.
Once a series of products have been extracted, and more products are added (typical deduplication scenario) the NETCDF GUNWs of the original products must be kept for processing to continue.

#download data
ariaDownload.py -t 64 -b '34.5 35.7 -116.5 -114.2' -s 20180101 -e 20180201 -o download

# inital default run
ariaTSsetup.py -f "products/*20180116_20180104*.nc" -w test_dir --verbose --log-level debug

# remove GUNWs for already extracted products
rm products/*20180116_20180104*.nc

# extract SET iteratively
ariaTSsetup.py -f "products/*.nc" -w test_dir --verbose --log-level debug -l 'solidEarthTide'

results in the error

Exception: ('Product not found: %s', '/Users/rzinke/Documents/ARIAdev/FwdProc-Dedup/SimTest/test_conda/products/S1-GUNW-A-R-064-tops-20180116_20180104-015014-00120W_00035N-PP-72fd-v3_0_1.nc')

Describe the solution you'd like
An error should not occur because the original products have already been extracted.
If the bbox expands or additional layers are requested, then the program should error out since the unextracted data are no longer available.