run_instance tweaks

We need to specify vpc as well as security groups when firing up instances.  Amazon doesn't support using security group names in those cases; you have to use the SecurityGroupId.  I added support for that edge condition.

While I was in there, added support for specifying a PrivateIpAddress as well.

Output of make test:

[paden@d0 net-amazon-ec2]$ make test
PERL_DL_NONLAZY=1 /usr/bin/perl "-MExtUtils::Command::MM" "-e" "test_harness(0, 'inc', 'blib/lib', 'blib/arch')" t/00_use.t t/01_init.t t/02_live.t t/03_failing_calls.t
t/00_use.t ............ ok     
t/01_init.t ........... ok   
t/02_live.t ........... ok     
t/03_failing_calls.t .. 1/5 $VAR1 = {
          'RequestID' => 'N/A',
          'Errors' => [
                      {
                        'Error' => {
                                   'Code' => 'HTTP POST FAILURE',
                                   'Message' => '500 Can\'t connect to localhost:22718 (Connection refused)'
                                 }
                      }
                    ]
        };


t/03_failing_calls.t .. ok   
All tests successful.
Files=4, Tests=76, 17 wallclock secs ( 0.04 usr  0.04 sys +  7.29 cusr  0.60 csys =  7.97 CPU)
Result: PASS