script: add a common ci_debug function to print ci debug lines

script: add a common ci_debug function to print ci debug lines

Reduces some of the boilerplate around emitting the "CI_DEBUG:"
prefixed debug lines for the CI. Additionally, enables using
the FORCE_CI_DEBUG var to enable ci debug lines even when not
in a jenkins environment.

Signed-off-by: John Mulligan <jmulligan@redhat.com>
(cherry picked from commit 93b94811cb10bb936c5abf87d708ae96d7939a8e)