Previously, Rook Agent and Discovery DaemonSet deployment didn't allow
adding nodeAffinity. This commit adds nodeAffinity spec to daemonSet
deployment, which can be configured through environment variables in
operator deployment yaml.

+ Support multiple LabelKey, each with multiple LabelValue
+ Support multiple LabelKey with no value
Signed-off-by: Umanga Chapagain <chapagainumanga@gmail.com>