mtu: Add MTU parameter to Routes

- Change route to update existing route
- MTU parameter added to AddRoute

Bug: 142892223
Test: unit test
Change-Id: I2164808ef628eb7c12e875f0bde7f5151bf6a5b5
Merged-In: Ie339d0cee5be12c2232a4631fed61219a0facc64
(cherry picked from commit e521f07e8b03102f1b510a3fb401993513d9c127)
4 files changed