1054496: fix url string parsing exception handling on register

Reproduce with:
(thanks to jsefler)

```
Steps to Reproduce:
[root@jsefler-7 ~]# subscription-manager register --username=testuser1 --password=password --org=admin --baseurl=http//hostname/prefix --force
Error parsing baseurl: None
Expected results:
Error parsing baseurl: Server URL has an invalid scheme. http:// and https:// are supported

[root@jsefler-7 ~]# subscription-manager register --username=testuser1 --password=password --org=admin --baseurl=https:// --force
Error parsing baseurl: None
Expected results:
Error parsing baseurl: Server URL is just a schema. Should include hostname, and/or port and path


[root@jsefler-7 ~]# subscription-manager register --username=testuser1 --password=password --org=admin --baseurl=https://hostname:PORT/prefix --force
Error parsing baseurl: None
Expected results:
Error parsing baseurl: Server URL port should be numeric


[root@jsefler-7 ~]# subscription-manager register --username=testuser1 --password=password --org=admin --serverurl=https:// --force
Error parsing serverurl: None
Expected results:
Error parsing serverurl: Server URL is just a schema. Should include hostname, and/or port and path


[root@jsefler-7 ~]# subscription-manager register --username=testuser1 --password=password --org=admin --serverurl=https://jsefler-f14-7candlepin.usersys.redhat.com:PORT/candlepin --force
Error parsing serverurl: None
Expected results:
Error parsing serverurl: Server URL port should be numeric


[root@jsefler-7 ~]# subscription-manager register --username=testuser1 --password=password --org=admin --serverurl=https:hostname/prefix --force
Error parsing serverurl: None
Expected results:
Error parsing serverurl: Server URL has an invalid scheme. http:// and https:// are supported
```