Specify variabes read in from GLDAS files.

Otherwise, extraneous variable "time_bnds" gets read in, and this variable has different dimensions ('time' and 'bounds'), than all other variables ('lat', 'lon', and 'time'). This prevents proper parsing of the dimensions.
2 jobs for update-gldas in 21 minutes and 13 seconds (queued for 1 second)
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passed #397158597
build

00:11:16

 
  Test
passed #397158598
test

00:09:56