Fix nut-scanner crash on nut server scan,

upscli_sslinit calls upscli_readline which might calls upscli_disconnect in case of error. upscli_disconnect frees ups->host and set it to NULL, so it is illegal to use ups->host after a call to upscli_sslinit.
Fix connect in multi-threaded environnement on AIX

Closes issue #42
Fix wrong errno reported by connect on Solaris

Closes issue #43
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