log uploader: fixed log directory name
log uploader: fixed log directory name

The directory containing the log files on the master was computed
based on the builder name, instead of the 'builddir' value
specified in master.cfg.

BUG=400871

Review URL: https://codereview.chromium.org/479763002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@290410 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build