Fix tests when running with RUST_TEST_THREADS=1

Author: Jethro Beekman

tests/testsuite/test.rs

@@ -316,7 +316,7 @@ test test_hello ... FAILED
 failures:
 
 ---- test_hello stdout ----
-[..]thread 'test_hello' panicked at 'assertion failed:[..]",
+[..]thread '[..]' panicked at 'assertion failed:[..]",
         )
         .with_stdout_contains("[..]`(left == right)`[..]")
         .with_stdout_contains("[..]left: `\"hello\"`,[..]")
@@ -366,7 +366,7 @@ test test_hello ... FAILED
 failures:
 
 ---- test_hello stdout ----
-[..]thread 'test_hello' panicked at 'assertion failed: false', \
+[..]thread '[..]' panicked at 'assertion failed: false', \
       tests/footest.rs:1[..]
 ",
         )
@@ -402,7 +402,7 @@ test test_hello ... FAILED
 failures:
 
 ---- test_hello stdout ----
-[..]thread 'test_hello' panicked at 'assertion failed: false', \
+[..]thread '[..]' panicked at 'assertion failed: false', \
       src/lib.rs:1[..]
 ",
         )