Fix non-interactive use of conditionals in Eshell

Fix non-interactive use of conditionals in Eshell

* lisp/eshell/esh-cmd.el (eshell-rewrite-if-command): Fix misplaced
't' symbol; it should be passed to 'eshell-invokify-arg'.
(eshell-do-eval): Pass 'synchronous-p' to recursive calls in some
missing cases.

* test/lisp/eshell/esh-cmd-tests.el (esh-cmd-test/if-statement,
(esh-cmd-test/if-else-statement)
(esh-cmd-test/if-else-statement-lisp-form)
(esh-cmd-test/if-else-statement-lisp-form-2)
(esh-cmd-test/if-else-statement-ext-cmd)
(esh-cmd-test/unless-statement)
(esh-cmd-test/unless-else-statement)
(esh-cmd-test/unless-else-statement-lisp-form)
(esh-cmd-test/unless-else-statement-ext-cmd): Use
'eshell-command-result-equal'.