Allow authorization also against insecure registries (at least for testing)

Description of the issue: Currently if registry offers only insecure access, there’s no way to authenticate against it (https://github.com/GoogleContainerTools/jib/blob/master/jib-core/src/main/java/com/google/cloud/tools/jib/registry/RegistryEndpointCaller.java#L165). It would be good for testing to be able to authenticate over http (partly because of #543).

Expected behavior: Parameter where user acknowledges that it’s very bad idea to send credentials over http, but still allowing that.

Steps to reproduce: Create local registry with authentication and without TLS.

Environment: Apache Maven 3.5.0 (ff8f5e7444045639af65f6095c62210b5713f426; 2017-04-03T22:39:06+03:00) Java version: 1.8.0_131, vendor: Oracle Corporation Default locale: en_US, platform encoding: Cp1252 OS name: “windows 7”, version: “6.1”, arch: “amd64”, family: “windows” jib-plugin version: 0.9.6

jib-maven-plugin Configuration:

<plugin>
	<groupId>com.google.cloud.tools</groupId>
	<artifactId>jib-maven-plugin</artifactId>
	<version>${jib.version}</version>
	<configuration>
		<from>
			<image>${jib.fromImage}</image>
		</from>
		<to>
			<image>${jib.toImage}</image>
		</to>
		<container>
			<ports>
				<port>${jib.applicationPort}</port>
			</ports>
		</container>
		<allowInsecureRegistries>${jib.allowInsecureRegistries}</allowInsecureRegistries>
	</configuration>
	<executions>
		<execution>
			<phase>compile</phase>
			<goals>
				<goal>build</goal>
			</goals>
		</execution>
	</executions>
</plugin>

Log output: Without allowInsecureRegitstries:

[ERROR] Failed to execute goal com.google.cloud.tools:jib-maven-plugin:0.9.6:build (default) on project jib-demo-project: Build image failed, perhaps you should use a registry that supports HTTPS or set the configuration parameter 'allowInsecureRegistries': Only secure connections are allowed, but tried to reach URL http://artifactory/project/baseImage/manifests/latest -> [Help 1]

With allowInsecureRegitstries:

[ERROR] Failed to execute goal com.google.cloud.tools:jib-maven-plugin:0.9.6:build (default) on project jib-demo-project: Build image failed, perhaps you should make sure your credentials for 'artifactory' are set up correctly: Unauthorized for http://artifactory/project/baseImage: 401 Unauthorized
[ERROR] {"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":null}]}

Additional Information: If this is not possible, at least error message should state that authentication (username+password) was not even used, because connection was made with http instead of https.

[Hi-Fi]

0.9.8 seems have fixed this, so now authentication is sent to both directions correctly.

[chanseokoh]

It seems worth having a discussion to sort out things around HTTP, HTTPS, and allowInsecureRegistries. For example about the behavior of allowInsecureRegistries,

• It falls back to HTTP if HTTPS fails for any reason (I believe), which includes invalid or unverifiable certificates. In the certificate case, some people may expect Jib should just completely ignore the certificate problem and proceed with HTTPS (which might be risky and they should know what they are doing), like what curl --insecure does. For example, if a port is explicitly given like localhost:5000 that accepts HTTPS, the 5000 port won’t accept HTTP at all.
• It falls back to HTTP only after HTTPS fails. When a failure occurs, in many cases it is unclear if it is HTTP or HTTPS that failed. Also, I wonder if there should be a way to set Jib to just start with HTTP, instead of having this fallback feature. sendCredentialsOverHttp might make things more confusing when combined with the current behavior of allowInsecureRegistries.