NIFI-6323 Changed URLs for splunk.artifactoryonline.com to use HTTPS (certificate validity warning in browsers, but command-line connection using openssl s_client is successful).
NIFI-6323 Changed URLs for XMLNS schema locations to use HTTPS (the XMLNS and schema identifier remain http:// because they are not designed to be resolvable).
NIFI-6323 Fixed Maven XML schema descriptor URLs.
This closes#3497
NIFI-5468 add keypasswd with the default of keystorepasswd for bc compatibility
NIFI-5468 Use ARG instead of ENV for PATH variables as those need to be controlled in the build
NIFI-5468 Use BASE_URL for the default case when MIRROR_BASE_URL is not defined (and replace ARCHIVE_BASE_URL)
This closes#2921
Signed-off-by: Andrew I. Christianson <andy@andyic.org>