Fix crash that can occur if CLI registration fails for an aliased command.

A recent memory leak fix in main/cli.c causes an ast_cli_entry's command
field to be freed and NULLed if ast_cli_register() fails. res_clialiases
was ignoring the return value of ast_cli_register() and was then passing
the NULL command off to a a hash function. This resulted in a crash.

The fix is not to ignore the erroneous return value. If ast_cli_register()
fails, then we do not continue trying to process the current alias.
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Merged revisions 377840 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 377842 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 377843 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@377844 65c4cc65-6c06-0410-ace0-fbb531ad65f3