[Gatt Test] Do not compare padding values

Comparing padding values of StoredAttribute causes tests failure as in
x86 architecture padding is not initiliazed properly

Test: atest GattCacheTest#stored_attribute_to_binary_service_test --
--abi x86
Bug: 264504557
Tag: #refactor

Change-Id: Id09bb64e2807d56fcda6aa4671ea9f9de5b7dac4