Connection port parsing

[memetb]

This issue is meant to address #1124

This is a subtle bug because it has practically no impact on the libvirt code base. It only affects libvirt here:

	if err := l.ConnectToURI(libvirt.ConnectURI(u.RemoteName())); err != nil {

Outside of this location, this bug only affects ssh_config settings by incorrectly passing the target as "hostname:portname" instead of "hostname" here:

	// configuration loaded, build tunnel
	sshClient, err := u.dialHost(u.Host, sshcfg, 0)
	if err != nil {
		return nil, err
	}

However, when a port override is specified in the ConnectionString, u.Host will contain the hostname.

[memetb]

The added unittest assertions in this PR reveal the problem here:

 === RUN   TestURI
    connection_uri_test.go:34: 
        	Error Trace:	/home/runner/work/terraform-provider-libvirt/terraform-provider-libvirt/libvirt/uri/connection_uri_test.go:34
        	Error:      	Not equal: 
        	            	expected: "hostname"
        	            	actual  : "hostname:2222"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1 +1 @@
        	            	-hostname
        	            	+hostname:2222
        	Test:       	TestURI