Fix script cache bug in the scripting engine.
This commit fixes a serious Lua scripting replication issue, described by Github issue #1549. The root cause of the problem is that scripts were put inside the script cache, assuming that slaves and AOF already contained it, even if the scripts sometimes produced no changes in the data set, and were not actaully propagated to AOF/slaves. Example: eval "if tonumber(KEYS) > 0 then redis.call('incr', 'x') end" 1 0 Then: evalsha <sha1 step 1 script> 1 0 At this step sha1 of the script is added to the replication script cache (the script is marked as known to the slaves) and EVALSHA command is transformed to EVAL. However it is not dirty (there is no changes to db), so it is not propagated to the slaves. Then the script is called again: evalsha <sha1 step 1 script> 1 1 At this step master checks that the script already exists in the replication script cache and doesn't transform it to EVAL command. It is dirty and propagated to the slaves, but they fail to evaluate the script as they don't have it in the script cache. The fix is trivial and just uses the new API to force the propagation of the executed command regardless of the dirty state of the data set. Thank you to @minus-infinity on Github for finding the issue, understanding the root cause, and fixing it.