Update ast_set_default_eid() to find more network interfaces.

As of Fedora 15, ethN is not the name of ethernet interfaces.  The names
are emN or pciN.  Update some code that searched for interfaces named
ethN to look for the new names, as well.  For more information about why
this change was made, see this page:

    http://domsch.com/blog/?p=455
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Merged revisions 353077 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 353078 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@353079 65c4cc65-6c06-0410-ace0-fbb531ad65f3