[config] ignore trailing blank lines of multiline value (RhBug:1722493)
[config] ignore trailing blank lines of multiline value (RhBug:1722493)

Parser supports multiline values. Example:
key = value first line
  value second line

If a line starts with whitespaces and it is not a section name,
it is treated as continuation of previous key=value line.

This commit ignores trailing blank lines. So newline characters
are trimmed out from the end of line.

rpm-software-management/libhif,rpm-software-management/libhif,rpm-software-management/libdnf,rpm-software-management/libhif,rpm-software-management/libdnf,hughsie/libhif,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libdnf,rpm-software-management/libhif,hughsie/libhif,hughsie/libhif