[zircon][tests] Extend timeouts in scheduler PI tests

Zircon's kernel-linked unit tests have a number of tests of the Priority
Inheritance implementation; the tests have short timeouts. Raise the
timeouts for threads exiting and for rendezvous, to allow the tests to
pass on Grunt Chromebooks (ex: HP Chromebook 14-db00030nr).

Tested:
k ut pi and k ut all on HP Chromebook 14 no long panic:

$ k cpu features
[00297.995] 01189:01210> Vendor: AMD
[00297.995] 01189:01210> Microarch: Bulldozer
[00297.995] 01189:01210> F/M/S: 15/70/0
[00297.995] 01189:01210> patch_level: 6006705
[00297.995] 01189:01210> Brand: AMD A4-9120C RADEON R4, 5 COMPUTE CORES 2C+3G
[00297.995] 01189:01210> Features: fpu sse sse2 sse3 ssse3 sse4.1 sse4.2 mmx avx avx2 fxsr xsave mon aesni clflush
[00297.995] 01189:01210> fsgsbase smep rdrand syscall nx huge rdtscp invar_tsc
[00297.995] 01189:01210> Properties:

$ k ut pi
[00083.559] 00000:00000> pi : Running 6 tests...
[00083.719] 00000:00000>   basic                 : PASSED (159574557 nSec)
[00083.731] 00000:00000>   changing priority     : PASSED (12076525 nSec)
[00085.736] 00000:00000>   long chains           : PASSED (2005062331 nSec)
[00085.947] 00000:00000>   multiple waiters      : PASSED (210688460 nSec)
[00086.093] 00000:00000>   multiple owned queues : PASSED (146293419 nSec)
[00086.106] 00000:00000>   cycles                : PASSED (13520778 nSec)
[00086.106] 00000:00000> pi : All tests passed (6/6) in 2547229379 nSec
[00086.110] 01189:01210>
$

$ k ut all
...
[00107.835] 01189:01210> SUMMARY: Ran 35 test cases: 0 failed
$

ZX-3849

Change-Id: I3a2b50267e9d14ccb1f27e9910184f68a66f3907
diff --git a/zircon/kernel/tests/pi_tests.cpp b/zircon/kernel/tests/pi_tests.cpp
index 0406be3..44e54f3e 100644
--- a/zircon/kernel/tests/pi_tests.cpp
+++ b/zircon/kernel/tests/pi_tests.cpp
@@ -437,7 +437,7 @@
         EXPECT_TRUE(allow_shutdown_.state(), "");
     }
 
-    constexpr zx_duration_t join_timeout = ZX_MSEC(200);
+    constexpr zx_duration_t join_timeout = ZX_MSEC(500);
 
     switch (state_) {
     case State::INITIAL:
@@ -508,7 +508,7 @@
 bool TestThread::WaitForBlocked() {
     BEGIN_TEST;
 
-    constexpr zx_duration_t timeout = ZX_MSEC(500);
+    constexpr zx_duration_t timeout = ZX_MSEC(1000);
     constexpr zx_duration_t poll_interval = ZX_USEC(100);
     zx_time_t deadline = current_time() + timeout;