fix(lnd log level): Fix lndLogGetLevel to apply the most-recent log level when none is detected
fix(lnd log level): Fix lndLogGetLevel to apply the most-recent log level when none is detected

In some cases, multi-line log output was output at its value for the first line,
but in the trace log in following lines. For example, in this output:

  zap:lnd  [DBG]  2018-06-17 18:30:35.051 [DBG] CRTR: New channel update applied: (*channeldb.ChannelEdgePolicy)(0xc420e74310)({ +0ms
  zap:lnd  [DBG]   SigBytes: ([]uint8) (len=71 cap=71) { +0ms
  zap:lnd  [DBG]   }, +0ms
  zap:lnd  [DBG]   sig: (*btcec.Signature)(<nil>), +0ms
  zap:lnd  [DBG]   ChannelID: (uint64) 1423834572626526208, +0ms
  zap:lnd  [DBG]   LastUpdate: (time.Time) 2018-06-17 18:30:26 -0500 CDT, +0ms
  zap:lnd  [DBG]   Flags: (lnwire.ChanUpdateFlag) 1, +0ms
  zap:lnd  [DBG]   TimeLockDelta: (uint16) 6, +0ms
  zap:lnd  [DBG]   MinHTLC: (lnwire.MilliSatoshi) 1000 mSAT, +0ms
  zap:lnd  [DBG]   FeeBaseMSat: (lnwire.MilliSatoshi) 1 mSAT, +0ms
  zap:lnd  [DBG]   FeeProportionalMillionths: (lnwire.MilliSatoshi) 10 mSAT, +0ms
  zap:lnd  [DBG]   Node: (*channeldb.LightningNode)(<nil>), +0ms
  zap:lnd  [DBG]   db: (*channeldb.DB)(<nil>) +1ms
  zap:lnd  [DBG]  }) +0ms
  zap:lnd  [DBG]   +0ms

Previously the first line would be marked DBG, while the others were marked TRC.

LN-Zap/zap-desktop,LN-Zap/zap-desktop,LN-Zap/zap-desktop