update logging, retries and allow setting number of retries for vault component

Closes #281 (closed)

Update initialize-gun.sh to retry vault login, retrieving the root key, and adding the target key to vault. Tested sections of added logic locally to not impact prod notary/vault.

Script used to test some of the logic

for i in $(seq 1 $NUM_RETRIES); do
        if [ -n "${TEST_TOKEN:-}" ]; then
                if ! curl -f -LO "${TEST_TOKEN}"; then
                        echo "failed to curl, retrying"
                        TEST_TOKEN=<working_link>
                        echo "${TEST_TOKEN}"
                        continue
                else
                        echo "successfully curled"
                        break
                fi
        else
                echo $i
        fi
        if [ $i -eq 3 ]; then
                TEST_TOKEN=<broken_link>
                echo "${TEST_TOKEN}"
        fi
done