test/drb/test_drbssl.rb: skip LeakChecker as openssl keeps /dev/random

and /dev/urandom intentionally.  OpenSSL::PKey::RSA.new opens the two
random generators and keeps the file descriptors.

93f99b681a/crypto/rand/rand_unix.c (L674)

They are detected by the LeakChecker as fd leak, but it is intentional.

http://rubyci.s3.amazonaws.com/graviton2/ruby-master/log/20200526T160005Z.log.html.gz
```
[  597/20199] DRbTests::TestDRbSSLAry#test_01 = 0.29 s
Leaked file descriptor: DRbTests::TestDRbSSLAry#test_01: 8 #<File::Stat dev=0x6, ino=11, mode=020666, nlink=1, uid=0, gid=0, rdev=0x109, size=0, blksize=4096, blocks=0, atime=2020-05-23 14:45:13.751999995 +0000, mtime=2020-05-23 14:45:13.751999995 +0000, ctime=2020-05-23 14:45:13.751999995 +0000>
Leaked file descriptor: DRbTests::TestDRbSSLAry#test_01: 9 #<File::Stat dev=0x6, ino=10, mode=020666, nlink=1, uid=0, gid=0, rdev=0x108, size=0, blksize=4096, blocks=0, atime=2020-05-23 14:45:13.755999995 +0000, mtime=2020-05-23 14:45:13.755999995 +0000, ctime=2020-05-23 14:45:13.755999995 +0000>
```

test/drb/test_drbssl.rb

@@ -59,6 +59,7 @@ end
 class TestDRbSSLAry < Test::Unit::TestCase
   include DRbAry
   def setup
+    LeakChecker.skip if defined?(LeakChecker)
     @drb_service = DRbSSLService.new
     super
     setup_service 'ut_array_drbssl.rb'

tool/lib/leakchecker.rb

@@ -4,6 +4,7 @@ class LeakChecker
 
   def initialize
     @fd_info = find_fds
+    @@skip = false
     @tempfile_info = find_tempfiles
     @thread_info = find_threads
     @env_info = find_env
@@ -63,7 +64,7 @@ class LeakChecker
       }
     end
     fd_leaked = live2 - live1
-    if !fd_leaked.empty?
+    if !@@skip && !fd_leaked.empty?
       leaked = true
       h = {}
       ObjectSpace.each_object(IO) {|io|
@@ -123,6 +124,7 @@ class LeakChecker
       }
     end
     @fd_info = live2
+    @@skip = false
     return leaked
   end
 
@@ -290,4 +292,8 @@ class LeakChecker
     end
     output.puts(*a)
   end
+
+  def self.skip
+    @@skip = true
+  end
 end