Skip SSL verification if adding record through cloudflare fails

Currently, EE proceeds with SSL validation even if adding record through CloudFlare fails. It should not proceed for verification, but instead should instruct users to add the DNS records and manually run `ee site ssl` to validate the SSL challenge.

```
Couldn't add dns record using cloudlfare API. Re-check the config values of `le-mail` and `cloudflare-api-key`.
Add the following TXT record to your DNS zone
Domain: _acme-challenge.example.com.
TXT value: a7LuHiWEKK5_zmnL8YWgWrxQlGF6EuZeG_t_ykINtr4

Wait for the propagation before moving to the next step
Tips: Use the following command to check the propagation

host -t TXT _acme-challenge.example.com.
Couldn't add dns record using cloudlfare API. Re-check the config values of `le-mail` and `cloudflare-api-key`.
Add the following TXT record to your DNS zone
Domain: _acme-challenge.example.com.
TXT value: 1LJ9H8S29BPfOYSPM-df-0kEuBa3X6O_IcwJYD2PhU4

Wait for the propagation before moving to the next step
Tips: Use the following command to check the propagation

host -t TXT _acme-challenge.example.com.
Waiting for DNS entry propagation.
Starting SSL verification.
Warning: The dns entries have not yet propogated. Manually check:
host -t TXT _acme-challenge.example.com
Before retrying `ee site ssl example.com`
```