Increase the number of linux_aura slaves.
Increase the number of linux_aura slaves.

This is in preparation of adding it to the CQ.

TBR=petermayo@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/11418054

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@168475 0039d316-1c4b-4281-b951-d872f2087c98

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