mesh: Cfg: Only update friend state if supported
mesh: Cfg: Only update friend state if supported

If Friend support is not available we should not modify the value of
cfg->frnd.

X-Original-Commit: b9d9547531ecd9e29e46aea4c58b69bbf2ca846d

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble