Replace "-" with "+" in UA-linux-old-kernel version string too

Required to be consistent with changes in https://github.com/dnanexus/dx-toolkit/commit/ade947e36de298e49cf788dbe5ec7ae09b93a0bd

PS: Although, we don't necessarily need this transformation for UA make process, since UA is versioned separately (which is semver compatible) from dx-toolkit. But if we keep https://github.com/dnanexus/dx-toolkit/commit/ade947e36de298e49cf788dbe5ec7ae09b93a0bd, then we need to make this change too.