Make all DockerRequirements hints

A few CWL-files list the DockerRequirement under requirements,
instead of hints, which precludes running the workflow as
`cwltool --no-container`. This has been fixed.

lofar-cwl/steps/ms_concat.cwl

@@ -54,10 +54,11 @@ outputs:
     outputBinding:
       glob: ms_concat.log
 label: ms_concat
-requirements:
-  - class: ShellCommandRequirement
+hints:
   - class: DockerRequirement
     dockerPull: 'lofareosc/prefactor:HBAcalibrator'
+requirements:
+  - class: ShellCommandRequirement
   - class: InitialWorkDirRequirement
     listing:
       - entry: $(inputs.msin)

lofar-cwl/steps/wsclean.cwl

@@ -41,7 +41,8 @@ outputs:
     outputBinding:
       glob: $(inputs.image_name)-image.fits
 label: WSClean
-requirements:
+hints:
   - class: DockerRequirement
     dockerPull: 'lofareosc/prefactor:HBAcalibrator'
+requirements:
   - class: InlineJavascriptRequirement

steps/find_skymodel_cal.cwl

@@ -68,7 +68,7 @@ requirements:
             
             skymodels = $(inputs.skymodels)
             max_separation_arcmin = $(inputs.max_separation_arcmin)
-            max_separation_arcmin = 1.0 if max_separation_arcmin else max_separation_arcmin
+            max_separation_arcmin = 1.0 if max_separation_arcmin is None else max_separation_arcmin
             extension = "$(inputs.skymodels_extension)"
             if skymodels is None:
                 skymodels = "/data/skymodels"