Made it so shared=false works properly in noauth

RM8126

noauth was making it so shared=false + no tenant filter was returning shared
networks even though shared was supposed to be filtered out. The reason why
a sentinel value (INVERT_DEFAULTS) is used instead of an additional parameter
was due to it being the path of least resistance. There are intentions to
eventually move the shared attribute to the model.
Merge pull request #187 from roaet/hide_shared

Made it so shared=false works properly in noauth