Fix add_instrumentation test.
Fix add_instrumentation test.

0x0mar/ngx_pagespeed,wanrui/ngx_pagespeed,wanrui/ngx_pagespeed,pagespeed/ngx_pagespeed,digideskio/ngx_pagespeed,pagespeed/ngx_pagespeed,0x0mar/ngx_pagespeed,digideskio/ngx_pagespeed