lock_machine: look up skylab on $PATH

Not all cipd installations go into /usr/local/bin/. Chrotomation3
appears to have it on its path:

mobiletc-prebuild@chrotomation3:~/$ which skylab
/usr/local/bin/skylab

So this should be a nop, and should be more flexible for people who
want to have their cipd bits elsewhere.

BUG=None
TEST=ran crosperf

Change-Id: If0aae16f123ac23dd015b3bf879c899e06e20901
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2177064
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
1 file changed