conman:  Replace 'iw scan' with 'wifi scan'.

65f96da is the corresponding commit for waveguide.  With both that
commit and this one, conman and waveguide will not be able to scan
simultaneously due to /bin/wifi locking, preventing race conditions.

Change-Id: Ide0bcd5e0c22661f67bf951961a4cb20e3f1823a
3 files changed