tests: bluetooth: tester: allow to add more CCCs

Specification states that: "Only one Client Characteristic Configuration
declaration shall exist in a characteristic definition." This was
wrongly understood as "Ony one CCC can exist in GATT Server". When we
add next characteristic `ccc_added` flag is cleared so next CC can be
added (for this characteristic).

Added array for CCC values so it's no longer shared between CCCs.

Signed-off-by: Krzysztof Kopyściński <krzysztof.kopyscinski@codecoup.pl>