Ensure bash shell executions close file descriptors

Currently Bolt::Shell::Bash will leaves open file
descriptors at the conclusion of execute(). The
file descriptions do fall out of scope at the conclusion
of the execute() method and the Ruby GC eventually closes
them. However, on a very busy Bolt invocation with lots of
short-lived Tasks or a number of Tasks running in parallel
(e.g. via background()) the number of open FDs before
garbage collection can get moderately high, hitting problems
on systems with low file descriptor limits.

!bug

* **Explicitly close Bolt::Shell::Bash file descriptors**

  Ensure file descriptors in Bolt::Shell::Bash are explicitly
  closed, helping to alleviate the chance of hitting file
  descriptor limits on systems with low defaults (e.g. Mac OS).

lib/bolt/shell/bash.rb

@@ -470,7 +470,10 @@ def execute(command, sudoable: false, **options)
             result_output.merged_output << to_print
           }
         rescue Errno::EAGAIN, EOFError
+        ensure
+          stream.close
         end
+        inp.close
         result_output.stdout << read_streams[out]
         result_output.stderr << read_streams[err]
         result_output.exit_code = t.value.respond_to?(:exitstatus) ? t.value.exitstatus : t.value
@@ -490,7 +493,7 @@ def execute(command, sudoable: false, **options)
         result_output
       rescue StandardError
         # Ensure we close stdin and kill the child process
-        inp&.close
+        inp.close unless inp.nil? || inp.closed?
         t&.terminate if t&.alive?
         @logger.trace { "Command aborted" }
         raise