Bug 1966138: Better seting of email profile field

Normally when we use set_profile_field() to set an email it will make
the existing primary email be renamed to the new one.
But if you already have a secondary email with the same value then
things go wrong as it tries to set your existing primary to the new
value rather than just make the secondary one the primary one

Change-Id: Ia82c24c7f8e18eaac8c5c7cfd648c6a4b50ec3c0
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>