cyclictest: Convert the offset of the alignment option to microseconds

The offset is specified in microseconds according to the
documentation, but, the microseconds to nanoseconds conversion is
missing so the effective offset has the unit of nanoseconds.

Signed-off-by: Anna-Maria Gleixner <anna-maria@glx-um.de>
Signed-off-by: John Kacur <jkacur@redhat.com>