git p4 test: wait longer for p4d to start and test its pid

git p4 test: wait longer for p4d to start and test its pid

Running tests at high parallelism on a slow machine, 5 sec is
not enough to wait for p4d to start.  Change it to 5 minutes,
adding an environment variable P4D_START_PATIENCE to shrink
that if needed in automated test environments.

Also check if the pid of the p4d that we started is still
around.  If not, quit waiting for it immediately.

Remove all the confusing && chaining and simplify the code.

Thanks-to: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>