Use place holder for main thread name in tests

Author: WiSaGaN

tests/bench.rs

@@ -187,7 +187,7 @@ test bench_hello ... ")
                        .with_stderr_contains(format!("\
 [COMPILING] foo v0.5.0 ({})
 [RUNNING] target[..]release[..]foo-[..]
-thread 'main' panicked at 'assertion failed: \
+thread '[..]' panicked at 'assertion failed: \
     `(left == right)` (left: \
     `\"hello\"`, right: `\"nope\"`)', src[..]foo.rs:14
 [..]

tests/install.rs

@@ -715,7 +715,7 @@ fn reports_unsuccessful_subcommand_result() {
                 execs().with_status(0).with_stdout_contains("    fail\n"));
     assert_that(cargo_process("fail"),
                 execs().with_status(101).with_stderr_contains("\
-thread 'main' panicked at 'explicit panic', [..]
+thread '[..]' panicked at 'explicit panic', [..]
 "));
 }