test: add Ginkgo/Gomega coverage for pkg/ddc/base (#5803)

* test: cover ddc base dataset setup and volume paths

Signed-off-by: Harsh <harshmastic@gmail.com>

* test: fix context key type in ddc base specs

Signed-off-by: Harsh <harshmastic@gmail.com>

* test: keep ddc base setup coverage test-only

Signed-off-by: Harsh <harshmastic@gmail.com>

* test: cover ddc base setup stub defaults

Signed-off-by: Harsh <harshmastic@gmail.com>

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Signed-off-by: Harsh <harshmastic@gmail.com>

Author: hxrshxz