Default rpc_mem to false for bazel

[gasgallo]

Fixes #709.

[lee-bin]

Thanks for the contribution!
However, as it will change the default behavior for qualcomm socs, there is something more that needs to done to make the change work.

1. cmake should also be fixed so that they work the same way.
2. Docs should be added to specify how to enable rpcmem for qualcomm socs.

[gasgallo]

@lee-bin please check the new commits