8167424: Various trivial fixes in build system
Reviewed-by: erikj, tbell

8156733: JIB fails to follow redirects
Summary: Make jib more resilient, let it follow redirects, and handle network hickups with 3 retries.
Reviewed-by: erikj
Contributed-by: Stefan Sarne <stefan.sarne@oracle.com>

8146002: Need to support mirrors for bootstrapping Jib
Reviewed-by: ihse, tbell

8145185: Rename JAB the build tool to JIB
Reviewed-by: ihse, tbell