Only check phoneStatusBarIcon if profile

We currently request getUserStatusBarIconResId very frequently. We only
need to do so if it is a profile, since all non-profiles have no status
bar icon anyway, nor should they. Indeed, the method calling this is
called updateProfileIcon(). Fixing this has two advantages:
* We log a warning each time we ask for a non-profile's icon, so this
will clear up logcat.
* isProfile() gets automatically cached, whereas phoneStatusBarIcon
doesn't, so this will be more efficient, since we'll bypass the call
whenever it's not a profile.

Test: atest SystemUITests:com.android.systemui.statusbar.phone.PhoneStatusBarPolicyTest
Flag: EXEMPT bugfix
Change-Id: Ic12606975a96f44c9ee62b1ec200255bd0e5620c