fix virParseVersionString with linux 3.0

linux 3.0 has no micro version number, and that is causing problems
for virParseVersionString.  The patch below should allow for:
  major
  major.minor
  major.minor.micro

If major or minor are not present they just default to zero.
We found this in Ubuntu (https://bugs.launchpad.net/bugs/802977)

AUTHORS

@@ -179,6 +179,7 @@ Patches have also been contributed by:
   Daniel Gollub        <gollub@b1-systems.de>
   David S. Wang        <dwang2@cisco.com>
   Ruben Kerkhof        <ruben@rubenkerkhof.com>
+  Scott Moser          <smoser@ubuntu.com>
 
   [....send patches to get your name here....]
 

src/util/util.c

@@ -1598,16 +1598,16 @@ virParseNumber(const char **str)
 int
 virParseVersionString(const char *str, unsigned long *version)
 {
-    unsigned int major, minor, micro;
+    unsigned int major, minor = 0, micro = 0;
     char *tmp;
 
-    if (virStrToLong_ui(str, &tmp, 10, &major) < 0 || *tmp != '.')
+    if (virStrToLong_ui(str, &tmp, 10, &major) < 0)
         return -1;
 
-    if (virStrToLong_ui(tmp + 1, &tmp, 10, &minor) < 0 || *tmp != '.')
+    if ((*tmp == '.') && virStrToLong_ui(tmp + 1, &tmp, 10, &minor) < 0)
         return -1;
 
-    if (virStrToLong_ui(tmp + 1, &tmp, 10, &micro) < 0)
+    if ((*tmp == '.') && virStrToLong_ui(tmp + 1, &tmp, 10, &micro) < 0)
         return -1;
 
     *version = 1000000 * major + 1000 * minor + micro;