git-p4 tests: cd to / before running python

The python one-liner for getting the current time prints out
error messages if the current directory is deleted while it is
running if using python3.

Avoid these messages by switching to "/" before running it.

This problem does not arise if using python2.

Signed-off-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-git-p4.sh

@@ -50,7 +50,7 @@ native_path() {
 # at runtime (e.g. via NTP). The 'clock_gettime(CLOCK_MONOTONIC)'
 # function could fix that but it is not in Python until 3.3.
 time_in_seconds() {
-	python -c 'import time; print int(time.time())'
+	(cd / && python -c 'import time; print(int(time.time()))')
 }
 
 # Try to pick a unique port: guess a large number, then hope