Comparators prefer containers through blocks, except when block power level is 15

if you place a comparator in front of a block with a container behind it, the comparator will output how full the container is, even if the block betwen is powered. For some reason if the block gets power 15 the comparator will also output 15 and not how full the container is.

Code analysis: https://bugs.mojang.com/browse/MC-64394?focusedCommentId=292104&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-292104