Record missing packages in the header

Journal header contains information about relevant package NVRs.
Previously, if a relevant package was not present on a system,
no information was recorded. Currently an information that the
package is missing is explicitly recorded.
rlLogDebug should not cause nonzero return code unless there is a problem with loging

If DEBUG mode is not enabled rlLogDebug ended with nonzero return code.
This could cause some unexptected behaviour for example with 'set -e' active.