RegistryAuth: handle case where password contains colon

[mattnworb]

Fixes #764. This now matches how docker-cli parses this field from
~/.docker/config.json.

[mavenraven]

@mattnworb what if the password contains 2 colons?

[mattnworb]

@mavenraven it will be taken care of by String.split(String, int):

The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n - 1 times, the array's length will be no greater than n, and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

[mattnworb]

btw seems like this bug existed before #759:

docker-client/src/main/java/com/spotify/docker/client/messages/RegistryAuth.java

Lines 189 to 194 in 55b993d

	final String[] authParams = Base64.decodeAsString(authString).split(":");
	if (authParams.length == 2) {
	authBuilder.username(authParams[0].trim());
	authBuilder.password(authParams[1].trim());
	} else if (serverAuth.has("identityToken")) {

[codecov-io]

Codecov Report

Merging #765 into master will decrease coverage by 0.06%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #765      +/-   ##
============================================
- Coverage      65.3%   65.23%   -0.07%     
+ Complexity      676      674       -2     
============================================
  Files           156      156              
  Lines          2957     2957              
  Branches        340      340              
============================================
- Hits           1931     1929       -2     
- Misses          877      878       +1     
- Partials        149      150       +1