[COMMON] Use "" instead of {} as a default value to avoid warning

[COMMON] Use "" instead of {} as a default value to avoid warning

After we upgraded our helm version we started getting below issues
with emails:

Warning: Merging destination map for chart 'curator'.
Overwriting table item 'image', with non table value:
onap/sdnc-image:1.8.2

To fix this let's just use "" instead of () for our daily operations.

Issue-ID: OOM-2412
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Change-Id: I5f2c215c281036a7eb921d6a805527c807a4aca9
(cherry picked from commit 8953675506f4b3807502a3be73b846ab5fe79c67)