Fix un-changeable resource in l3_if_downup

The previous patch attempted to change @resource[:wait_carrier_after_ifup]
 this dosn't work. This patch changes this to create a new variable to test
 before entering into the carrier wait loop

Change-Id: I1f6e8d8eff253dc665a66bf64f1d2ecfedb1f63a
Related-bug: #1275132
Merge "Fix un-changeable resource in l3_if_downup"