Restore string cancellation test

The cancel on-going task with string id test was failing in CI because
of a race condition involving server log messages. We need to wait for a
notification that the project has been compiled before we wait for the
"Waiting for" message, otherwise we might pick up the "Waiting for"
message from the previous test case and try to cancel the task before it
has been created.

server-test/src/test/scala/testpkg/EventsTest.scala

@@ -54,6 +54,9 @@ object EventsTest extends AbstractServerTest {
     svr.sendJsonRpc(
       s"""{ "jsonrpc": "2.0", "id":$id, "method": "sbt/exec", "params": { "commandLine": "run" } }"""
     )
+    assert(svr.waitForString(10.seconds) { s =>
+      s contains "Compiled events"
+    })
     assert(svr.waitForString(10.seconds) { s =>
       s contains "Waiting for"
     })
@@ -66,13 +69,15 @@ object EventsTest extends AbstractServerTest {
     })
   }
 
-  /* This test is timing out.
   test("cancel on-going task with string id") { _ =>
     import sbt.Exec
     val id = Exec.newExecId
     svr.sendJsonRpc(
       s"""{ "jsonrpc": "2.0", "id": "$id", "method": "sbt/exec", "params": { "commandLine": "run" } }"""
     )
+    assert(svr.waitForString(10.seconds) { s =>
+      s contains "Compiled events"
+    })
     assert(svr.waitForString(10.seconds) { s =>
       s contains "Waiting for"
     })
@@ -84,5 +89,4 @@ object EventsTest extends AbstractServerTest {
       s contains """"result":{"status":"Task cancelled""""
     })
   }
- */
 }