Revert "Set the atrace clock to boot when possible and mono otherwise."

This change broke CTS tests.

This reverts commit 56a2ba0b.

Bug: 37906221
Test: cts-tradefed run singleCommand cts-dev --module
CtsAtraceHostTestCases passes locally.
Change-Id: Ia82732eac33fbde8bddc1e8de7a68c20befe760e