textproc/elasticsearch{5,6}: Fix symlink

Relative symlinks should only be used when both files are in the
STAGEDIR. In this situation poudriere was producing usable packages
because of the unique location of WRKSRC (/wrksrc/...) which caused the
relative symlink to be deep enough "../../../../../" to hit the root of the
filesystem and then point to the location of the file. However, users
who were building the port directory with "make" or "portmaster" were
getting symlinks that did not point to the right location.

PR: 226234 226265 222261