NEXUS-5744: fix for redirect strategy

There was initially a "prevent redirection to index pages"
check that proved to be overly broad. It was meant to prevent
redirections like:

http://host/path -> http://host/path/

as "path" is actually a collection (directory in HTTP lingo)
on server side, and this is usual redirections that HTTP
servers do when asked for that 1st URL: redirect to "index page"
of the given collection.

But, this check was too broad, as it prevented redirections
like

http://hostA/path/ -> http://hostB/path/

for example (same for HTTP -> HTTPS or even port change
redirections), as it was checking only that 2nd URL does not end with slash.


Related issue:
https://issues.sonatype.org/browse/NEXUS-5744