* On my device (AP7901 / AOS v3.9.0 / App v3.7.4) discovery would keep
clobbering the bank and current sensor. Looking in to it the oid
should be used for current and not bank. To fix this now it pulls
a count of banks using the `rPDULoadDevNumBanks.0` oid. Per MIB that
will return 0 if no banks are found. In which case skip the bank
detection.
* Also update PowerNet-MIB to v4.1.7 released 2015-08-05