ignore newlines in dpkg-deb control output for installing debs

ignore newlines in dpkg-deb control output for installing debs

Leading or trailing newlines can be confusing for our parser as it
expects two newlines to start/stop a new stanza. To solve this the lines
we wanna add are printed first, ignore any leading newlines and then add
the stanza as provided by dpkg-deb with or without trailing newlines as
the parser will look at the first stanza only anyway and removing
trailing newlines is considerably harder to do.

Closes: 802553