mod: bump version of kvdb submodule
mod: bump version of kvdb submodule

PR #5992 was merged without a bump in the kvdb version which results in
an error when trying to pull in lnd 0.14.0-beta as a library in other
projects.

We'll need to push the kvdb/v1.2.1 tag _after_ merging this PR.

aakselrod/lnd,aakselrod/lnd