udevadm: fix option parsing breakage with klibc

udevadm: fix option parsing breakage with klibc

The klibc implementation of getopt_long() behaves slightly different
from the glibc one - in particular, it treats the change of the option
string argument between invocations as start of parsing a different
command line, and resets its state.  However, the udevadm code
expected getopt_long() invocations in subcommands to continue parsing
the rest of command line after initial options has been parsed at the
top level; with klibc this broke, causing all udevadm subcommands to
stop recognizing their options.

Instead of relying on the glibc behavior, reset the getopt_long()
state properly before invoking the subcommand handler: move argv to
point to the subcommand name, decrease argc appropriately, and set
optind = 0.  This also fixes a minor bug visible with glibc - without
setting optind = 0 all getopt_long() calls in subcommand handlers were
behaving as if "+" was specified as the first character of the option
string (which disables option reordering), because that state was set
by the first getopt_long() call at the top level, and was not reset
when parsing subcommand options.

Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>