Resove issue with ignored region argument 

Resolves: https://github.com/saltstack/salt/issues/14752

## Tests Performed - Automated
### Ubuntu 12.04
ran tests in both us-east-1 and us-west-1 regions
```./tests/runtests.py -n unit.modules.boto_secgroup_test```
### Ubuntu 14.04
ran tests in both us-east-1 and us-west-1 regions
```./tests/runtests.py -n unit.modules.boto_secgroup_test```

## Tests Performed - Manual:
Test success condition for all publicly exposed methods.
```
salt-call boto_secgroup.create boto_name boto_description region=us-east-1 --log-level debug
salt-call boto_secgroup.exists boto_name region=us-east-1 --log-level debug
salt-call boto_secgroup.exists not_boto_name region=us-east-1 --log-level debug
salt-call boto_secgroup.delete boto_name region=us-east-1 --log-level debug
salt-call boto_secgroup.create boto_name boto_description region=us-east-1 --log-level debug
salt-call boto_secgroup.authorize boto_name region=us-east-1 ip_protocol=tcp from_port=80 to_port=80 cidr_ip='["10.0.0.0/0", "192.168.0.0/0"]' --log-level debug
salt-call boto_secgroup.get_config boto_name region=us-east-1 --log-level debug
salt-call boto_secgroup.revoke boto_name region=us-east-1 ip_protocol=tcp from_port=80 to_port=80 cidr_ip=10.0.0.0/0 --log-level debug
salt-call boto_secgroup.get_config boto_name region=us-east-1 --log-level debug

salt-call boto_secgroup.create boto_name boto_description region=us-west-1 --log-level debug
salt-call boto_secgroup.exists boto_name region=us-west-1 --log-level debug
salt-call boto_secgroup.exists not_boto_name region=us-west-1 --log-level debug
salt-call boto_secgroup.delete boto_name region=us-west-1 --log-level debug
salt-call boto_secgroup.create boto_name boto_description region=us-west-1 --log-level debug
salt-call boto_secgroup.authorize boto_name region=us-west-1 ip_protocol=tcp from_port=80 to_port=80 cidr_ip='["10.0.0.0/0", "192.168.0.0/0"]' --log-level debug
salt-call boto_secgroup.get_config boto_name region=us-west-1 --log-level debug
salt-call boto_secgroup.revoke boto_name region=us-west-1 ip_protocol=tcp from_port=80 to_port=80 cidr_ip=10.0.0.0/0 --log-level debug
salt-call boto_secgroup.get_config boto_name region=us-west-1 --log-level debug
```
And, yes, confirmation that I didn't miss any regions:
```
cjohnson04:salt cjohnson$ grep -ir '_get_group' salt/modules/boto_secgroup.py
salt/modules/boto_secgroup.py:    group = _get_group(conn, name, vpc_id, group_id, region)
salt/modules/boto_secgroup.py:def _get_group(conn, name=None, vpc_id=None, group_id=None, region=None):
salt/modules/boto_secgroup.py:    group = _get_group(conn, name, vpc_id, region)
salt/modules/boto_secgroup.py:    sg = _get_group(conn, name, vpc_id, group_id, region)
salt/modules/boto_secgroup.py:    group = _get_group(conn, name, vpc_id, group_id, region)
salt/modules/boto_secgroup.py:    group = _get_group(conn, name, vpc_id, group_id, region)
salt/modules/boto_secgroup.py:    group = _get_group(conn, name, vpc_id, group_id, region)
```