tests: Add scapy as a required program

The utils.subr file includes a couple of subroutines
(ping_dummy_check_request and ping_server_check_reply) that require
scapy.

Add this requirement in the header of each test that makes use of them.

Reported by:	Jenkins
Reviewed by:	kp, ngie
Approved by:	emaste (mentor)
Differential Revision:	https://reviews.freebsd.org/D48917

tests/sys/netpfil/pf/fragmentation_pass.sh

@@ -443,6 +443,7 @@ no_df_head()
 {
 	atf_set descr 'Test removing of DF flag'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 no_df_body()
@@ -481,6 +482,7 @@ reassemble_slowpath_head()
 {
 	atf_set descr 'Test reassembly on the slow path'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 reassemble_slowpath_body()
@@ -609,6 +611,7 @@ dummynet_fragmented_head()
 {
 	atf_set descr 'Test dummynet on NATed fragmented traffic'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 dummynet_fragmented_body()

tests/sys/netpfil/pf/max_states.sh

@@ -31,6 +31,7 @@ max_states_head()
 {
 	atf_set descr 'Max states per rule'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 max_states_body()

tests/sys/netpfil/pf/route_to.sh

@@ -516,6 +516,7 @@ ifbound_reply_to_head()
 {
 	atf_set descr 'Test that reply-to states bind to the expected interface'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 ifbound_reply_to_body()
@@ -571,6 +572,7 @@ ifbound_reply_to_v6_head()
 {
 	atf_set descr 'Test that reply-to states bind to the expected interface for IPv6'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 ifbound_reply_to_v6_body()
@@ -630,6 +632,7 @@ ifbound_reply_to_rdr_dummynet_head()
 {
 	atf_set descr 'Test that reply-to states bind to the expected non-default-route interface after rdr and dummynet'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 ifbound_reply_to_rdr_dummynet_body()

tests/sys/netpfil/pf/src_track.sh

@@ -132,6 +132,7 @@ max_src_conn_rule_head()
 {
 	atf_set descr 'Max connections per source per rule'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 max_src_conn_rule_body()
@@ -191,6 +192,7 @@ max_src_states_rule_head()
 {
 	atf_set descr 'Max states per source per rule'
 	atf_set require.user root
+	atf_set require.progs scapy
 }
 
 max_src_states_rule_body()