Allow empty resources for CPU and Memory in Katib config

[andreyvelich]

Fixes: #1559.
This will allow to specify empty resources for CPU and Memory in Katib config.

/cc @gaocegege @johnugeorge @sravi999

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In response to this:

Fixes: #1559.
This will allow specify empty resources for CPU and Memory.

/cc @gaocegege @johnugeorge @sravi999

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[johnugeorge]

/lgtm
Do we have any tests just to check this?