watchfrr: Allow end users to turn off watchfrr for a particular daemon

watchfrr: Allow end users to turn off watchfrr for a particular daemon

Allow an end user who is debugging behavior, with say gdb, to turn
off watchfrr and it's attempts to keep control of a daemons up/responsiveness

With code change:
donna.cumulusnetworks.com# show watchfrr
watchfrr global phase: Idle
  zebra                Up
  bgpd                 Up/Ignoring Timeout
  staticd              Up

Now grab bgpd with gdb:

sharpd@donna ~/frr4> date ; sudo gdb -p 27893
Mon 16 Sep 2019 01:44:57 PM EDT
GNU gdb (GDB) Fedora 8.3-6.fc30
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word".
Attaching to process 27893
[New LWP 27894]
[New LWP 27895]
[New LWP 27896]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
0x00007f1787a3e5c7 in poll () from /lib64/libc.so.6
Missing separate debuginfos, use: dnf debuginfo-install glibc-2.29-15.fc30.x86_64 gperftools-libs-2.7-5.fc30.x86_64 json-c-0.13.1-4.fc30.x86_64 libcap-2.26-5.fc30.x86_64 libgcc-9.1.1-1.fc30.x86_64 libgcrypt-1.8.4-3.fc30.x86_64 libgpg-error-1.33-2.fc30.x86_64 libstdc++-9.1.1-1.fc30.x86_64 libxcrypt-4.4.6-2.fc30.x86_64 libyang-0.16.105-1.fc30.x86_64 lua-libs-5.3.5-5.fc30.x86_64 lz4-libs-1.8.3-2.fc30.x86_64 pcre-8.43-2.fc30.x86_64 xz-libs-5.2.4-5.fc30.x86_64
(gdb)

In another window we can see when watchfrr thinks it's not responding:

donna.cumulusnetworks.com# show watchfrr
watchfrr global phase: Idle
  zebra                Up
  bgpd                 Unresponsive/Ignoring Timeout
  staticd              Up

Finally exit gdb and watchfrr now believes bgpd is good to go again:

donna.cumulusnetworks.com# show watchfrr
watchfrr global phase: Idle
  zebra                Up
  bgpd                 Up/Ignoring Timeout
  staticd              Up

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>