proxy: in proxy tunnels, use the smaller timeout value of #380

Job	Run time
Empty APLOGNO() test	38s
Default	3m 56s
All-static modules	3m 58s
Prefork MPM, all-modules (except cgid)	4m 24s
Worker MPM, all-modules	5m 27s
Shared MPMs, all-modules	4m 32s
Event MPM, all-modules, mod_cgid only	4m 59s
Event MPM, all-modules, no CMSG_DATA	4m 24s
Default, all-modules + install	6m 23s
Default, all-modules, random test order	4m 32s
GCC 10 maintainer-mode w/-Werror, install + VPATH	4m 51s
All-modules, APR 1.7.4, APR-util 1.6.3	5m 25s
APR 1.8.x, APR-util 1.7.x	6m 40s
Pool-debug	6m 38s
Shared MPMs (event), pool-debug, SSL/TLS variants	11m 6s
Shared MPMs (worker), pool-debug, SSL/TLS variants	10m 35s
Shared MPMs (prefork), pool-debug, SSL/TLS variants	10m 39s
litmus WebDAV tests	2m 26s
Regenerate ap_expr	5m 12s
APR 1.7.4, APR-util 1.6.3, LDAP	4m 31s
APR trunk thread debugging	5m 10s
UBSan	6m 54s
ASan	7m 20s
ASan, pool-debug	7m 50s
HTTP/2 test suite	13m 21s
MOD_TLS test suite	6m 8s
	2h 37m 59s

Provide feedback