python-common: make count & count-per-host >= 1 checks consistent

python-common: make count & count-per-host >= 1 checks consistent

The previous version of the validate function had a incorrect error
statement that suggested the count must be >1  when it should have
been >=1. This confusion was possibly due to using "n < 1" on
one line and "n <= 0" on another line. Since both values are supposed
to be integers this change corrects the error message and makes
the comparisons on the lines both use "n < 1" (since I find it easier
to see that the check "n < 1" is the inverse of the error text
asserting "n >= 1").

Signed-off-by: John Mulligan <jmulligan@redhat.com>