Correct defining dicts using yaml's anchors

Correct defining dicts using yaml's anchors

This commit corrects previous mistake assuming that
parameter's nested content derived via "<<" operator
can be overwritten with single value, while in practice,
whole key would be change.

For practical explanation, following entry:
a: &a
 b: 1
 c:
  d: 2
  e: 3
x:
 <<: *a
 c:
  d: 10

Would yield following content:
a:
 b: 1
 c:
  d: 2
  e: 3
x:
 b: 1
 c:
  d: 10

And as we can see, "e" key is missing there.
This commit correct this.

Issue-ID: SDNC-1122
Signed-off-by: Konrad Bańka <k.banka@samsung.com>
Change-Id: I15dfe0219ee1d6bcde7d29821ed2650bc8698244