This bug came about because of three issues that this change
corrects:
- The CI scripts run on a pull request did not test building
  Helm. This means that a failure to set a variable using LDFLAGS
  had no opportunity to be caught.
- #8608 provided a means to match the k8s version used in linting
  and chartutil with the version of the package we pull in. With
  one problem. It attempts to set a const as if it were a string.
  This is ignored and everyone missed it.
- #10325 moved those constants to vars so it could be set. This
  looked good and passed tests but missed that you can't set an
  int as if it were a string. See first bullet.

This change fixes this by moved the internal representation to
be a string. These are internal variables not exposed in the public
API which makes this change non-breaking to the API.

Closes #10367
Signed-off-by: Matt Farina <matt.farina@suse.com>