test: turn USR_BIN_TIME into a lazy prerequisite

Two test scripts (t3302 and t3419) had copy & paste code to set
USR_BIN_TIME prerequisite.  Use the test_lazy_prereq helper to define
them in the common t/test-lib.sh.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3302-notes-index-expensive.sh

@@ -9,7 +9,6 @@ test_description='Test commit notes index (expensive!)'
 
 test_set_prereq NOT_EXPENSIVE
 test -n "$GIT_NOTES_TIMING_TESTS" && test_set_prereq EXPENSIVE
-test -x /usr/bin/time && test_set_prereq USR_BIN_TIME
 
 create_repo () {
 	number_of_commits=$1

t/t3419-rebase-patch-id.sh

@@ -6,7 +6,6 @@ test_description='git rebase - test patch id computation'
 
 test_set_prereq NOT_EXPENSIVE
 test -n "$GIT_PATCHID_TIMING_TESTS" && test_set_prereq EXPENSIVE
-test -x /usr/bin/time && test_set_prereq USR_BIN_TIME
 
 count()
 {

t/test-lib.sh

@@ -859,6 +859,10 @@ test_lazy_prereq EXPENSIVE '
 	test -n "$GIT_TEST_LONG"
 '
 
+test_lazy_prereq USR_BIN_TIME '
+	test -x /usr/bin/time
+'
+
 # When the tests are run as root, permission tests will report that
 # things are writable when they shouldn't be.
 test -w / || test_set_prereq SANITY