Revert "connman: Remove connman.service file"

removing the service file breaks the nfs-boot functionality, hence reverting

This reverts commit 6b3707197b5f021973ee79dac03dd4dc22e6d6d7.
Merge pull request #243 from fahadusman/revert_remove-connman-service-file

Revert "connman: Remove connman.service file"