Standardize format for parameter names

[derekargueta]

They're mostly camelcase but there's a few odd snakecase instances - log_dir and log_backtrace_at, and also some that don't do any casing at all i.e. alsologtostderr and stderrthreshold

➜  fbtracert -help
Usage of fbtracert:
  -addrFamily string
    	The address family (ip4/ip6) to use for testing (default "ip4")
  -alsologtostderr
    	log to standard error as well as files
  -baseSrcPort int
    	The base source port to start probing from (default 32768)
  -jsonOutput
    	Output raw JSON data
  -log_backtrace_at value
    	when logging hits line file:N, emit a stack trace
  -log_dir string
    	If non-empty, write log files in this directory
  -logtostderr
    	log to standard error instead of files
  -maxColumns int
    	Maximum number of columns in report tables (default 4)
  -maxSrcPorts int
    	The maximum number of source ports to use (default 256)
  -maxTTL int
    	The maximum ttl to use (default 30)
  -maxTime int
    	The time to run the process for (default 60)
  -minTTL int
    	The ttl to start at (default 1)
  -numResolvers int
    	The number of DNS resolver goroutines (default 32)
  -probeRate int
    	The probe rate per ttl layer (default 96)
  -showAll
    	Show all paths, regardless of loss detection
  -srcAddr string
    	The source address for pings, default to auto-discover
  -stderrthreshold value
    	logs at or above this threshold go to stderr
  -targetPort int
    	The target port to trace to (default 22)
  -tosValue int
    	The TOS/TC to use in probes (default 140)
  -v value
    	log level for V logs
  -vmodule value
    	comma-separated list of pattern=N settings for file-filtered logging