Reduce wait time in SubprocessTest.CancelTest am: 15a6ead86b am: 02832209e2

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1371997

Change-Id: Ib79a534300aab4b45ef8d13edc7d24e0393f4b8f
diff --git a/common/subprocess_unittest.cc b/common/subprocess_unittest.cc
index e71d3d8..74fee61 100644
--- a/common/subprocess_unittest.cc
+++ b/common/subprocess_unittest.cc
@@ -280,7 +280,7 @@
   // This test would leak a callback that runs when the child process exits
   // unless we wait for it to run.
   brillo::MessageLoopRunUntil(
-      &loop_, TimeDelta::FromSeconds(120), base::Bind([] {
+      &loop_, TimeDelta::FromSeconds(20), base::Bind([] {
         return Subprocess::Get().subprocess_records_.empty();
       }));
   EXPECT_TRUE(Subprocess::Get().subprocess_records_.empty());