rpm: more reliable detection of CentOS 7.4.

rpm/SPECS/nginx-module.spec.in

diff --git a/rpm/SPECS/nginx-module.spec.in b/rpm/SPECS/nginx-module.spec.in
index 028b179..dfc4f86 100644
--- a/rpm/SPECS/nginx-module.spec.in
+++ b/rpm/SPECS/nginx-module.spec.in
@@ -13,10 +13,11 @@
 %endif
 
 %if 0%{?rhel} == 7
+BuildRequires: redhat-lsb-core
 %define epoch 1
 Epoch: %{epoch}
-%define openssl_version %(rpmquery openssl | cut -c 9-13)
-%if "%{openssl_version}" == "1.0.2"
+%define os_minor %(lsb_release -rs | cut -d '.' -f 2)
+%if %{os_minor} >= 4
 %define dist .el7_4
 %else
 %define dist .el7

rpm/SPECS/nginx-plus-module.spec.in

diff --git a/rpm/SPECS/nginx-plus-module.spec.in b/rpm/SPECS/nginx-plus-module.spec.in
index cbce094..2922019 100644
--- a/rpm/SPECS/nginx-plus-module.spec.in
+++ b/rpm/SPECS/nginx-plus-module.spec.in
@@ -13,8 +13,9 @@
 %endif
 
 %if 0%{?rhel} == 7
-%define openssl_version %(rpmquery openssl | cut -c 9-13)
-%if "%{openssl_version}" == "1.0.2"
+BuildRequires: redhat-lsb-core
+%define os_minor %(lsb_release -rs | cut -d '.' -f 2)
+%if %{os_minor} >= 4
 %define dist .el7_4
 %else
 %define dist .el7

rpm/SPECS/nginx.spec.in

diff --git a/rpm/SPECS/nginx.spec.in b/rpm/SPECS/nginx.spec.in
index 422735e..b9d938b 100644
--- a/rpm/SPECS/nginx.spec.in
+++ b/rpm/SPECS/nginx.spec.in
@@ -26,14 +26,15 @@
 %endif
 
 %if 0%{?rhel} == 7
+BuildRequires: redhat-lsb-core
 %define _group System Environment/Daemons
 %define epoch 1
 Epoch: %{epoch}
 Requires(pre): shadow-utils
 Requires: systemd
 BuildRequires: systemd
-%define openssl_version %(rpmquery openssl | cut -c 9-13)
-%if "%{openssl_version}" == "1.0.2"
+%define os_minor %(lsb_release -rs | cut -d '.' -f 2)
+%if %{os_minor} >= 4
 Requires: openssl >= 1.0.2
 BuildRequires: openssl-devel >= 1.0.2
 %define dist .el7_4