Selectively disable iCloud keychain syncing for WiFi passwords
Solution 1:
Unfortunately I can offer no perfect solution however I can confirm this shortcoming in the iCloud Keychain sync. I've been able to reproduce this same behavior. Indeed a selective disabling ability in the keychain settings would do the trick. Until Apple implements functionality like that I think your options are
- turning off wi-fi on your phone when your near that hotspot
- turning off iCloud Keychain sync on your phone.
Because iCloud Keychain was delayed from the original release of iOS 7 I'm guessing Apple just didn't have time to implement finer grain controls on what is and isn't synced.
Solution 2:
I was able to stop my MacBook from using a wifi password that should only be used on the iPhone by going into KeyChain Access -> System -> UNWANTED_WIFI_NETWORK -> Access Control and then removing airport and airportd from the list "Always allow access by these applications". Seems to be still connecting on the iPhone but not the MacBook.