Keyguard: fix statusbar lags when default widget shown.

When statusbar became expanded KeyguardStatusView receives
onKeyguardVisibilityChanged callback and refreshes ClockView.
Because it receives more than one call and every time it reads
new values from resources it cause lags in opening statusbar panel.

Replace this code with BroadcastReceiver and ContentObserver to
refresh it only in case something was changed.

Change-Id: If0dbc1db059536806852661931cb2e6436f2acf4
Turn off carrier provisioning by default

Whether or not to use carrier provisioning is a setting hidden to the
end user that is currently not set. Unfortunately, on some carriers that
may result in it being set to yes, or effectively set to yes, without
other accompanying changes that must occur, such as setting a tethering
apn and possibly having a carrier provisioning app, resulting in hitting
a paywall when a tethering plan exists, or, worse having nothing happen
at all when you try to tether since the data doesn't have an apn set.

Change-Id: I3b5b3cc86e3325302411f46e3fd5f7a7c1b9f57e