fix: ServiceMonitor PodMonitor scrape config null values

[shkrid]

Description

When using liqo's ServiceMonitors and PodMonitors with ArgoCD we encounter unresolvable diff with null values.
ArgoCD failed to sync this resources.

How Has This Been Tested?

Deployed new version -> ArgoCD does not show wrong diff.

[adamjensenbot]

Hi @shkrid. Thanks for your PR!

I am @adamjensenbot.
You can interact with me issuing a slash command in the first line of a comment.
Currently, I understand the following commands:

• /rebase: Rebase this PR onto the master branch (You can add the option test=true to launch the tests
  when the rebase operation is completed)
• /merge: Merge this PR into the master branch
• /build Build Liqo components
• /test Launch the E2E and Unit tests
• /hold, /unhold Add/remove the hold label to prevent merging with /merge

Make sure this PR appears in the liqo changelog, adding one of the following labels:

• kind/breaking: 💥 Breaking Change
• kind/feature: 🚀 New Feature
• kind/bug: 🐛 Bug Fix
• kind/cleanup: 🧹 Code Refactoring
• kind/docs: 📝 Documentation

[aleoli]

/rebase test=true

[aleoli]

/merge