LRWD: combine failure reason to one

Connection failures are counted separately in 3
categories: association, authentication, and DHCP failures.
Sum the three counts in one for watchdog trigger.

Bug: 123349476
Test: ./frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Test: adb shell dumpsys wifi and verify following

Change-Id: I80a62f36d7cf682c98604d0fd2d2c3ac63f97b2d
2 files changed