Improves test stability

src/ruby/.rspec

 -I.
 -Ipb
+--backtrace
 --require spec_helper
 --format documentation
 --color

src/ruby/lib/grpc/generic/rpc_server.rb

@@ -417,18 +417,18 @@ module GRPC
         begin
           an_rpc = @server.request_call(@cq, loop_tag, INFINITE_FUTURE)
           c = new_active_server_call(an_rpc)
+          unless c.nil?
+            mth = an_rpc.method.to_sym
+            @pool.schedule(c) do |call|
+              rpc_descs[mth].run_server_method(call, rpc_handlers[mth])
+            end
+          end
         rescue Core::CallError, RuntimeError => e
           # these might happen for various reasonse.  The correct behaviour of
           # the server is to log them and continue, if it's not shutting down.
           GRPC.logger.warn("server call failed: #{e}") unless stopped?
           next
         end
-        unless c.nil?
-          mth = an_rpc.method.to_sym
-          @pool.schedule(c) do |call|
-            rpc_descs[mth].run_server_method(call, rpc_handlers[mth])
-          end
-        end
       end
       @running = false
       GRPC.logger.info("stopped: #{self}")

src/ruby/spec/client_server_spec.rb

@@ -28,7 +28,6 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 require 'grpc'
-require 'spec_helper'
 
 include GRPC::Core
 
@@ -47,7 +46,7 @@ shared_context 'setup: tags' do
   end
 
   def deadline
-    Time.now + 2
+    Time.now + 5
   end
 
   def server_allows_client_to_proceed

src/ruby/spec/pb/health/checker_spec.rb

@@ -179,7 +179,6 @@ describe Grpc::Health::Checker do
 
   describe 'running on RpcServer' do
     RpcServer = GRPC::RpcServer
-    StatusCodes = GRPC::Core::StatusCodes
     CheckerStub = Grpc::Health::Checker.rpc_stub_class
 
     before(:each) do