read_targets in 1.1.1 not properly reading SV3 MTL ledgers

[araichoor]

thanks to an issue reporting from Eddie:

the ['SV3_DESI_TARGET', 'SV3_BGS_TARGET', 'SV3_MWS_TARGET', 'SV3_SCND_TARGET'] columns are not read anymore when one reads the SV3 MTL ledgers with the 1.1.1 tagged version:

with 1.1.1:

>>> import desitarget
>>> desitarget.__version__
'1.1.1'
>>> from desitarget.io import read_targets_in_box
>>> d = read_targets_in_box("/global/cfs/cdirs/desi/survey/ops/surveyops/trunk/mtl/sv3/dark", radecbox=[270,271,60,61], mtl=True)
>>> [key for key in d.dtype.names if key[:3]=="SV3"]
[]

with 1.0.1:

>>> import desitarget
>>> desitarget.__version__
'1.0.1'
>>> from desitarget.io import read_targets_in_box
>>> d = read_targets_in_box("/global/cfs/cdirs/desi/survey/ops/surveyops/trunk/mtl/sv3/dark", radecbox=[270,271,60,61], mtl=True)
>>> [key for key in d.dtype.names if key[:3]=="SV3"]
['SV3_DESI_TARGET', 'SV3_BGS_TARGET', 'SV3_MWS_TARGET', 'SV3_SCND_TARGET']

[geordie666]

Addressed in #755.